A few ideas...
- make fossils out of salt clay/play-doh and toy dinosaurs-- make tracks or imprints of their bodies.
- enclose little toy dinosaurs in salt dough with sand or coffee grounds (google for a recipe) in it. dry and then bring to class so kids can smash them open.
- papermache dinosaur bones-- use TP rolls, wads of tissue/newspaper at the ends and masking tape to make the bone shape. then cover with the papermache-- or you can decoupage strips of tissue paper-- use white glue diluted with water (or coffee to dye a light brown)
Hope that helps!