Bones? Spoons? Gourd rattles? Woodblocks? Getting parents involved with a "make-it" "take-it" instruments workshop. Involve the local library who may have a lecturer on tap (oops, sorry, this is likely to be you) or resources on how to make your own simple instruments.

Maybe even the comb and tissue paper - or as simple as two sticks or marbles/nuts or popcorn in a jar, shaken. Check out - the Chenille Sisters (Ann Arbor, MI) - they do some children's concerts and have "instruments" on stage the kids can play with no starting knowledge.

Best of luck! Elaine