Beef ribs are fine. I'd go lightly on the cake, but every now and then won't hurt them. I give stale leftover dessert to mine on occasion, when it doesn't all get eaten up too fast.
I don't think it's good idea to feed the chocolate. Alot of people talk about how they got away with it and their chickens were fine, but if they get enough of it, it can make them sick or possibly kill them. be safe.