H.B.
Turn them into a matching game. Put a sticker on one can and the letter that it starts with on another can. There are so many possibilites you can do with the memory game idea; match lower case letters with uppercase letters, match numbers with corresponding dots, things that go together, etc. Have fun and let your boys help.
As far as crafts you could cut shapes out of sponges and glue them to the can to make stamps that you can paint with.