Children go back to Mexico and when the turn 18 they get a one time shot a citizenship including a real ssn and registering for the draft. If they wait too long, past their 19th birthday they forfeit any chance at head of the line immigration privileges. Just one of the pack,
I think I would offer the children the choice of whether to stay or go, possibly with an age bracket. Those younger than teen-age go, per your suggestion. Teen-age or older could choose to stay, with a responsible citizen sponsor/foster parent, and then are eligible to your suggestion above.
My reasoning here is that the younger kids, if not bilingual, can probably make the language "switch" easily. The teens would likely have great difficulty.