We are the Dinosaurs

The boys are dinosaurs–sometimes Tyrannosaurus Rexes, sometimes three horns, sometimes Spike, and sometimes they just growl. It is fun to wake up to three-year-old asking to play dinosaurs and then be greeted by a growling ten-month-old. The sandbox is filled with sand and dinosaurs, winter dinosaur pj's are the hippest (and dirtiest) trend, the oldest will eat his protein if he's pretending to be a sharp tooth (after all, no good herbivore would eat chicken). It only presents one problem. How do you convince a sharp tooth dinosaur that pretend biting is better than real biting?