Some kind of badge worn around the child's neck would be more practical. Both would be good . The seatbelt for the first responders and the one on the kid for the nurses and doctors.
Aye, it doesn't matter what it is, just something they are comfortable with. Then again, that would require training... and guess what? That ain't gon' happen in the US.
I don't care how much it helps, if they don't want it there it's entirely de-humanizing.