As far as the ‘celestial garden’, I was using that as a metaphor for whatever spiritual reality in which these still-born or aborted babies presently reside. I agree with your assesment that the Adamic Garden appears to have been on earth.
The definition of immortality descibes something that is not subject to death. As you well know from the story, Adam could eat from every tree of the Garden (including the Tree of Life), so as long as he steered clear of the one forbidden tree, as “in the day that thou eatest thereof thou shalt surely die”. But notice something even in his state of innocence. All was not good in the Garden. Adam was nevertheless discontent because he was alone. God made us to interact with other beings. His spiritual progress could not progress until then.
For though little ones whose life has been cut short, I’m sure they are receiving the kind of interactions with others beings, either others who have passed on or angelic beings, so that their spiritual development can progress as well. Unless you believe in ‘soul sleep’ I don’t think they are just floating around in limbo somewhere.
Besides all that, immortality doesn’t mean we are disembodied spirits. We are promise one day to receive a spiritual body, one that is not corrupt. And I’m confident it will have the same essence as the body Jesus was raised up in. Don’t forget that Jesus was in a mortal body, yet did not sin.
Maybe you are thinking that these babies would not have the opportunity to experience temptation or sin. Maybe you are right. But that doesn’t discount the possibility of being raised in a sinless state and growing thereby nonetheless. I’m sure righteous angels learn things, too (I Peter 1:12).
I have a question for you, though, Michael. Does our ability to choose between right and wrong disappear when we are ressurrected into immortality? If not, what will keep us from making the wrong choice once we get there?
ETA: I am also entertaining the idea that the first resurrection involves everyone in two groups: 1) Those that are ‘in Christ’ past and present", who will reign with Christ 1000 years IN RESURRECTED IMMORTAL SPIRITUAL BODIES, including still-born and aborted babies and 2) everyone else that is resurrected but who were without Christ or never had a chance to hear the gospel residing outside the city with a second chance (or first chance as it may be) to repent during the millinial reign.