I think it depends on what your family would enjoy. On our trip last month we did dinner at both. Cape May, to me, has better food. You have some good seafood options like crab legs and fish fillets and chowder, as well as items for those you don't like seafood (my wife doesn't eat seafood and enjoys Cape May). The food isn't the best, but it's better than Chef Mickeys. Both, by the way, have some fun dessert options.
Chef Mickeys, of course, has characters. While my DD8 liked eating the crab legs at CMC (and cracking them open even more - she started to do mine, too), seeing Mickey, Minnie, etc. was better to her. Your kids are a bit older than mine on the whole, so that needs to factor in.
All of this, then, doesn't answer your question. If I had to pick only one, I'd probably do Chef Mickeys just for the joy on the kids' faces when they spot Mickey for the first time. But neither one is a bad choice.