☆.A.
I just wanted to mention something that a friend did at her son's dinosaur party that was really cool and the kids (boys and girls) loved it!
She made little plaster chunks with prizes inside that they could use little chisels, brushes, etc. to reveal.
OR I have heard of getting a bunch of bones from the butcher, boiling, baking & cleaning really well & hiding them in a big sand pile or sand box....