Mike,

Some general camping info stuff that I've always thought about - mostly because I'm paranoid and also because I like to be comfortable (and my wife and I are backpackers, so take this FWIW):

• For your sleeping bags, either purchase cocoons from someone like REI or take nice cotton sheets as well. Many of the bags are some sort of nylon or polyester and tend to stick if you're sweaty. Having the extra stuff helps to serve as a buffer for that sweat and a lighter cover if it's warmer out.
• Thermarests or some sort of foam padding is your friend. Your back and wife will thank you.
• Plenty of water. Even if it's just one night, realize that if you don't have water, you'll need more than you think. Even when backpacking, I like to have 6L per day (big overkill, but I drink a lot of water). You need it for cleaning, drinking, food prep, etc., so having extra isn't a bad thing - especially as you're not carrying it.
• Have some Nalgene or other very portable containers for the water in case there's hiking or activities that aren't right on top of a water source.
• If the item's critical, carry a spare.
• Having a good folding knife, a whistle, some waterproof matches, a plastic signalling mirror, and a decent first aid kit are all a must. Even if it's just a day and a night, prepping as if something will go wrong is a good thing.
• You may want to bring a day pack to carry around some stuff for you and your family. That way they aren't without or they don't have to go back to the vehicle.
• Make sure you've got trail mix, snack bars that aren't chocolate, and that sort of quick finger food available for the kids.
• If anyone's allergic to bee stings and the like, make sure you've got the remedy stuff (be it the self-injector or benadryl tabs) readily at hand.

Probably overkill and I'm sure I've left stuff off of here, but there you go.