You can fish in the big lake (Bay Lake); however, it cost $$$$$ for the fishing trip. Lots to do at the campground ... movie, sing-a-long, pool, canoeing, paddleboat, bikes, playgrounds, etc.
Suggest you take the time to just ride the boats between the resorts (e.g. WL/FW/Contemporary) - there is also a boat that goes between Poly/MK/GF.
I really enjoy these and they are "free".