To aerate in the winter, you basically use the same system that you use in the summer, just move the diffuser to approximately 1/4 the total pond depth. 8' deep pond? Have the diffuser at 2' depth for the winter. Just move the diffuser so it keeps the ice thawed all the way to shore. That way, if anything (or anybody) go for a swim mid-winter, they can reach the shore to get out and not have to climb back up on the ice.
If your sons want to fish, have them use single hooks and have the hooks barbless (or pinch the barb down). Use a net to get the fish out of the water and keep handling to a minimum. Try and get the fish back into the water as fast as possible.
If they fish a lot, and the fish get educated, switch from artificials to live bait, but watch for them swallowing the hook. If the fish get hook shy, they might have to be replaced with less smart fish.