Lotta boats out there that could fit the bill, but the size will be dictated more by the RV he plans to pull it behind. Length limits in all states and some that don't allow "doubles" at all. The longer the tow vehicle/trailer...the shorter the boat needs to be. I haul my tracker behind my 5th wheel, and in some states I'm illegal. Some things to think about anyway.
A good stable deep V seems like the ticket if they want to do some big water fishing. Just my 2 cents.