You are exactly right, the packing and un-packing and cleaning of everything was time consuming, having everything already loaded, all you add are some clothes and food and away you go is much more enjoyable.
Conserving water is valuable if you go Dry Camping, but not necessary if you are going to KOA's or established RV Parks with full hook ups.
If you are going to be "Dry Camping", or going where there is no water/electricity/or sewer hook ups, then definitely begin to think about ways to conserve water, but it really depends how long you will be camping. I would say a full 25 gals of internal water, plus a couple gallons of drinking water would be plenty, but the kids need to know not to keep flushing the toilet!

You will want to bring separate drinking water only because the tanks in your trailer will leave the water with a slight plastic taste and while it is not dangerous, I would bet your kids might object to drinking it, or brush teeth with it. We have done 2 such trips but they were just for the weekend and we didn't have a problem. If you think about it, a gallon jug of water is enough to cook dinner with, a couple gallons could wash dishes and you have a 25 Gallon tank for clean water. You can also bring extra water in the car, and 2 or 3 extra gallons in the trailer. (Remember every gallon of water weighs 8 lbs, so don't over load.)
While the dry camping was fun because we could be off by ourselves, the full hookup places are usually where we go. We spent Christmas a couple years ago at
http://www.pismocoastvillage.com/ . We were a couple hundred feet from the ocean, full electrical/water/wifi/waste dump at each spot. There is something to be said for convenience. Also remember if you dry camp you will have to find a Dump Station to empty the Black Water Tank.
I would advise going to full hook up sites at first and get experience with your trailer, then maybe plan a weekend trip up to a lake, or secluded spot to try dry camping. I bet there are hundreds of beautiful spots in Washington, I am jealous you are closer to the ocean than we are. One big problem with AZ is no matter where you go, it is dusty and dirty, even up around Flagstaff, and everything gets covered in dirt.
Sorry for the long post, I am a mechanical Engineer, so I tend to ramble on about details.