I found this interesting idea which would be good for parents as an add-on for a magic-themed birthday party:

For this cool child activity, put a black-top hat in the middle of a large room and have all the kids sit in a circle around the hat. Then pass out an equal number of playing cards to each kid and have them take turns tossing the cards into the hat.

(Change the size of the circle, closer or farther away from the hat, to match the skill and patience level of the kids).

Each kid in turn tosses a card into the hat. If they get theirs in they continue to toss until they miss. The player who tosses the most cards into the hat gets to start the next round