It's a pretty small RV, so you won't be spending much time inside at all, I'd just remove the futon, and then you have a perfect area for the twins.
If you do geta rainy day and need to be inside, fold up the pack and plays, and use a few nice folding camp chairs as seating. Gander mountain camp chairs are actually pretty nice.
When the kids get older, you can put the futon back in that they can sleep on.
Since you won't be spending as much time inside, get a nice easy up and a good patio map or 2. Great place for the kids to play.
I don't spend any time inside my camper either, and do all my cooking outside. Invest in a good set up for outdoor cooking. Like a folding kitchen from Cabellas, coleman stove and grill, and you've got an outside kitchen as nice as the built in ones on the larger RVs.