I'm guessing you're talking about the "Build a Dinosaur" at the T-Rex restaurant? I haven't been to the one at DTD, but I have been to one in Kansas City twice. The "Build a Dinosaur" is exactly like "Build a Bear Workshop" but without as many choices.
Both times we went my DS, who was 6 the first time and 7 the second didn't do the build a dino, but they have a pretty good "gift shop." If you have a little boy who loves dinosaurs there is a lot to choose from and it's not too pricey. We bought two stuffed dinosaurs (not the ones you make) for about $8 each and the second time we went, DS picked out game that's like "Operation" except you pull out the bones and if you touch the sides the dinosaur roars.
Warning: Food is pricey for what you get