Yeah, any message of hope for the shooting would have to involve post-mortem salvation at least, which could be dicey. A great way to introduce the consolation of UR, of course, and several important theological emphases connected with that, but not a topic to bring up unless you want to go the distance. Moving on then…
Hm. Not many direct UR themes in the Nativity stories. Very broad scope, especially for GosMatt’s outcaste shepherds and probably-pagan astrologers, but not a lot about God saving all His enemies. In fact the various hymns in GosLuke tend to have a theme of “Yay, God is finally going to save us righteous Israelites, it’s about time!” 
I’ve been doing a commentary project on the Gospels (not yet having posted much of it), the next portion of which would be the Nativity stories, which is why I know things are a bit sparse there. 
Some of the OT scriptural references are interesting: Gabriel’s message to Zechariah about John quotes Malachi 4, which John himself strongly references later in his ministry, which in connection with Malachi 3 (the chapters are the same in the Jewish Bible I think) indicates that the coming wrath of God on all sinners is to purify and save them. But this topic in itself doesn’t seem to be referenced in Luke 1. (The connections are much stronger in John’s Synoptic preaching scenes later.)
The “name of Jesus” theme could be extrapolated on: to deny that God saves anyone from their sins is literally to deny the name of Jesus, which we’re warned about later in the Gospels–but not here. (Alternately, to ask who “His people” are, trying to find exclusions whom He did not come to save, smacks of the lawyer’s question “And who is my neighbor?” But again, not really a theme here in the nativity stories.)
The “Course of Abijah” timing could indicate a conception around Dec 25 and thus a birth 40 weeks later for the Feast of Tabernacles, which is itself connected to the Day of Atonement. We know some obscure things about that, of course–how the day of Atonement was for everyone, and how some Jews thought no one would have to spend more post-mortem punishment than a year maximum before being processed through the Day of Atonement. But that would require a lot of setup and is a bit speculative; nor does it seem to be a theme of the Gospel nativities themselves. Also, challenging when Jesus was actually born?–not something I’d recommend as a guest preacher for a Christmas weekend sermon to traditionalists.
I do rather like the translation of Zechariah’s hymn where he says,
“that we, being rescued
from the hand of our enemies,
might offer Him fearless and divine service
in kindness and fair-togetherness
before Him, for all our days!”
That’s something a little unusual worth building a Christmas sermon on, I’d say.
It also has some topical connections to God’s covenant with Abraham to keep faith with Abraham’s heirs, a covenant God went out of His way to ensure that only He signed onto, not Abraham, so that the sins of Israel would not nullify the covenant! But to unpack that would take a while, and the full force of it would require a lot of digression into the Epistle to the Hebrews.
The end of Zechariah’s hymn, on the other hand, is more immediately suggestive. “Those who sit in darkness and under the shadow of death” were supposed to be the pagans, but Zechariah applies it to Israel, thus acknowledging that in their rebellions Israel became like the pagans; consequently, the salvation promised by the covenant of God to Abraham (a covenant of fullest scope which God graciously ensured could not be broken on the human side, and which God will not break) applies to the Gentiles as well as to the Jews, as the Evangelists themselves make note of later in the Gospels! There are some strong (although very tacit) connections to universal salvation there, including post-mortem salvation: sitting in darkness under the shadow of death is emblematic of hades/sheol/tartarus, too.
If the Birth takes place at the beginning of the Tabernacles feast, that would easily explain the shepherds being out in the fields watching over their flocks: it helps prevent them from being stolen by thieves! Jesus later in GosJohn, during one of His Tabernacle Feast discourses with opposing rabbis, distinguishes Himself as the Good Shepherd from rebel/thieves who break into the fold to steal, sacrifice, and kill. (The Greek there isn’t usually translated accurately.) This provides some strong topical constraints to how to interpret GosMatt 25: the (baby) goats there are part of Christ’s flock, too; and to claim that He “apollums” (kills/destroys/loses) His own flock, runs against the promises of GosJohn!–moreover, to try to present God as someone Who sacrifices and kills the sheep for His own sake, as though this is appropriate to His glory, is tantamount to trying to flatter God as a rebel brigand, which gets the person who tries it in the preceding parable of Matt 25 (about the talantons of silver) thrown out into the darkness where the goats are going!
But that may be rather too extensive and challenging for a short sermon.
You’re welcome to borrow a sermon I wrote for the Cadre Journal back in 2010, if you like, on translating “Peace among men of His delight” and how that could still be good news. Paidion and I debated somewhat over how the term at the end of that phrase was best translated, and I thought he scored some good points, but if he’s right it certainly doesn’t hurt my argument.
Simeon in the Temple (who may have been intended to be a cameo by Simeon son of Hillel and father of Gamaliel I!) sings,
"My eyes have seen Your Salvation
"Which You are making ready to fit
"the face of all the peoples!
"Yes, the Light (as it is written) ‘for the revelation to the nations’
“and the glory of Your people Israel!”
Note that some English translations obscure the meaning there by translating instead as “Your Salvation which You have prepared in the presence of all people.” Preparing salvation in the presence of everyone isn’t the same as preparing salvation for everyone!–and the more literal rendering indicates that God is preparing (through the Son) to conform all people (or at least all people-groups) to Himself!
Simeon’s citation is a phrase from several places in Isaiah–9:2; 42:6; 49:6, 9; 51:4; 60:1-3, and maybe elsewhere, too. I haven’t checked them yet, but we all know Isaiah’s a good book to go hunting UR testimony in. 
I seem to recall offhand that chapter 42 is especially pertinent on that topic.
Simeon’s quiet warning to Mary, that Jesus “is appointed for the fall and the rising of many in Israel”, could have a meaning similar to Paul’s in Romans 11, that those who still are stumbling over the stumbling stone have not stumbled so as to fall but will be eventually raised and saved with everyone else. (But to be fair it might be a contrast comparison instead: the fall of the great and the rise of the oppressed righteous.)
Matthew’s appeal to Jeremiah 31:15 as prophecying the Slaughter of the Innocents, is rather interesting because the actual prophecy has nothing in the least to do with innocent children being slain by an enemy of God and everything to do with righteous Israel (as Rachel) weeping over her rebel children (typified as wayward daughters and even more importantly as Ephraim, probably in reference to Absalom, David’s rebel son slain in the forests of Ephraim, speared while hanging from a tree with a bleeding scalp 
, for whom David would rather have died instead) slain by God for their sins! God, in comforting Rachel who will not be comforted, promises that He has not forgotten Ephraim, that He still loves him, and that Ephraim will learn to repent from this and so be restored to Rachel by God!–which can only be post-mortem salvation of rebels punished to death by God! This portion of prophecy ends with God saying that He will accomplish this somehow by some new thing He will be doing which involves a woman encompassing a man: in hindsight, that seems awfully like a riddled prophecy of the Virgin Birth!
That’s pretty much all I’ve got. Good luck!–maybe someone else will have some more useful suggestions.
But then again I’ve spoken, even sung, in front of large groups of people before, and somehow managed it okay 
