Ugh, dealing with raw meat in the kitchen is so challenging. There's some fun to be had for sure, but at the same time, how do you prevent cross-contamination? (#nobodylikessalmonella)
Here's one easy way I've let my kiddo get involved with preparing chicken: Bust out the tenderizer. Full disclosure: This requires some supervision because mine is seriously heavy-duty. But he's engaged.
Here are a couple ideas for making it easier/safer:
Use a Ziploc bag. Usually you'd put the meat between two pieces of plastic wrap, but with a child, there's a good chance those pieces of meat are going to fly right out of there. A bag is less frustrating for all involved.
Place something under the meat. I use a metal baking sheet. This way, if he slips, he's not banging my counter with a heavy-duty meat tenderizer.