Do you have a small gas grill? Or did you intend to always cook over the charcoal grill at the site? I'm big on the convenience and speed of gas when we're camping and in sightseeing mode.
And I second the good air mattress and chairs.
However, do you have any friends with an Aero Bed that you could borrow? They're the kind of thing that is awesome to have (a good, high-quality brand) but you don't use often, so it is nice to lend. We have a king size and I have a friend with a queen size. If we ever go tenting or have a big sleepover party for DS in the basement, I borrow her queen size. Thanksgiving comes around and her family is in town and she borrows our king size. Works great.
Folding chairs are handy for camping and lots of other things as well.