A small power meter to check the quality of the power from the power pole. Trust me, I lost a microwave because the pole was putting out too may volts.
I would carry a small brass "y" coupler for the for the water. I have been at camps that had one water supple per 4 campers but you had to supply your own divider.
Something to look at for the future.... A blue tote to carry excess black/grey water. Some of my favorite camps to do not have sewer.
A torpedo level.
A refrigerator fan to improve the cooling ability.... Might even consider a kit to improve it.
A water cooler. Cuts down on water bottles and cooler space.
A good cooler.... Pre-freeze your ice... Don't just buy that bag and put in in your cooler.
A good easy to clean grill. I have this one and I love it http://reviews.basspro.com/2010/5847...ws/reviews.htm
First aid kit
Zero gravity chairs are SO much better than bag chairs
Bucket light. You'll love it!
Small entry way carpet.
Dollar store fabric softener for the toilet.
45 clear bend for the potty hose
Small fire starter logs. $.99 at Walmart per log.
Small broom and pan pan
Baby wipers are gold
That are just a few things to start thinking about.