This would be a great project to do with any age. I took huge balloons and covered them with homemade paper mache' (cooked flour and water, with a bit of liquid starch added). I used newspaper to wrap them. I put 3 layers on each day for 3 days. After they dried for a few more days, I cut the balloons in half with a box cutter and took out the plastic balloons (there is a one year old little brother, so we can't have plastic balloon pieces!!), leaving only the newspaper and paper mache'. I filled them with plastic dinosaurs and dinosaur tattoos (I was cheap and didn't really fill them full...).
I covered them with paper mache' soaked tissue paper in greens, whites, and blues... After cake cutting, I looked out in the yard and said, "Oh my! There is something over in the bushes! You guys come out and see what it is!" We had pre-made a nest out of limbs, sticks, and branches. The children ran over and each got an egg to crush open. They had a ball beating them and ripping them apart. :)
On the way home from our party, my precious niece said, "I can't believe that dinosaurs came to Aunt Sha-sha's house!"