I have a friend here even larger than the guy you describe - he is in his mid-seventies now and has no difficulty getting in and out of my PA28.
That said I would have to say front seat only and have the children sitting behind him so with the seat back no leg room issues for an adult behind.
Agree also - PA28 4 place - mine is s 181 with a Warrior going to be fun getting it off the ground assuming normal sized people - assuming not full fuel.