Any kind of adult bike should be fine. I would suggest a standard adult mountain bike (like you might get from Kmart) for the purposes you are suggesting, especially if he hasn't been riding for quite a while. The other thing I would suggest is to go and buy a extra wide seat (I call them 'fat bum seats', because they are alot more comfortable for my fat bum) and swap them over - it will make the ride alot more comfortable. You may need to pick up the wide seat from a bike shop, I am not sure whether the larger department stores have them as a general stock item.