Yes, they can interbreed. Will they? Probably not.
Even if they do, a bluegill/redear hybrid can be a very desirable fish. I've had thousands of them and they are beautiful, fast growing, and take to pelleted feed quite well.
Generally speaking, if the water is clear, and there isn't a ton of competition for spawning areas the bluegill and redears will breed true to their own species. It's something I really wouldn't worry too much about.
