I'm assuming you're camping in an established campground and not trying to backpack into the deep woods for your first trip. If so, you'll be able to pack everything into your vehicle, so don't worry about space.
The best thing to take is definitely an air mattress!! And don't forget a portable pump for it. There are several battery operated pumps on the market, or if you'd like to include a thigh work out, there are foot pumps, too.
In Alaska we call it "bug dope" but the rest of the world calls it insect repellant. For adults, get the highest concentration of DEET you can find. Apply liberally to clothing, sparingly to skin. For children (or pregnant/lactating women), a citronella based product is best. Cutters (US name) makes a coiled bracelet that my 2 year old daughter loves. She wears it around her neck instead of her wrist, but it keeps the bugs off.
You'll also want to make sure you have plenty of water. Don't worry about taking too much, what you don't use you can always store for next time. Or water the plants when you get home. I'd recommend at least a gallon per person (US measure, sorry, we're still not metric!) per day.
And don't forget toilet paper! You'll need it out in the woods... or even in an outhouse.