Super Cabs (I always knew them as club cabs) were great compared to just the regular cab. I didn't know they made them any more, but I haven't been looking at a new truck since I got my 2005 crew cab.
If all you're going to do is taking another couple out to dinner from the RV park, the the club cab would probably work - depends on how much hassle it is to get in and out of it. It won't be near as easy as opening a rear door for either people or just to put groceries in. I think it won't hold up as well on resale value either.
I'd go with the crew cab.
Bill