B.C.
It's not something I ever worried about.
As the kids leave the party, you give them a bag, and since all bags hold the same things and look more or less the same, you're not taking time to search for a particular bag and everyone it out the door happy with a minimum of fuss.
Seriously, kids open them, play with the stuff for a few days and the bags are in the trash in less than a week.
It's not worth the time/expense/effort over something that's gone so fast.