I haven't made one yet since our munchkins are past that age but saved some charms for gifts. A lot of quilters get the variety they need by swapping fussy cut charms. If you have some local gals who all want to do the same project, it's a great way to make this project economical. Basically, you just have to decide if you want to have a matching eye spy or all different pieces and the layout design you'd like. If you don't have anyone to trade with or prefer to find unique pieces, smaller cuts will do the trick. Sometimes you can find charm packs online that other quilters made up to save yourself some time.
Have fun!
Heather