For myself if I have started prepping food or crafts and child is not here I do not prep for them. If they show up during that time or during they don't get snack at all or are given plain paper and markers.

My late child was showing up right as everyone was sitting down. I quit scrambling to get something for him. I just let him go play while the others ate. Pretty soon drop offs became after snack as mom realized I wasn't feeding him if she walked in right at snack time.