Having trout year round would be dependant on having a strong spring in the ponds if it gets that warm in the summer. Anything above 65 degree water temperature for a long period of time will likely kill the trout. They may survive up to 70-75 but I'm not sure how well they'd do in a heavy stocked pond at that temperature without lots of aeration. Trout and bluegill can survive together but trout prefer and thrive in much cooler water than bluegill, so they probably wouldn't be a good mix for what he's looking to do.

As far as feeding scraps, some fish may eat it but it's not a good idea. Different feeds are made for different fish, it'd be best to get one well suited to whatever he decides to raise.

Rainbows from a hatchery will be better to raise as food than the cutthroats from a local stream. They'll already be conditioned to accept feed and it won't be depleting a wild fishery.