you should probably read about the intro to the game before you say this. but i mean i guess if they had a flash back mission or something, then it would be ok. but other than that, read the intro..
You mean playing as a kid in a flashback? Sure, I guess.
I wouldn't really consider one mission to be "playing as a kid".
As far as I know, you, the courier, have been shot in the head. Twice. And left in the desert to die. You were rescued by a robot named Victor. Being shot in the head (twice) you have no memory of who you are or what you were carrying. Only that someone wanted what you had bad enough to kill for it.
If this is anything like previous Bethesda games (I know, it's an Obsidion game) your character will have nearly no back story. Leaving you to "start from scratch" as it were. It is unlikely that there will be any flashbacks or any real way to find out who you were before being shot in the head.
I may be wrong. You may not be suffering from amnesia. But I don't expect to learn much of anything about the Courier's back story either way.
My point is that I doubt there will be flashbacks. And without flashbacks I don't think that there is any real chance of playing as a kid.