It's a matter of adaptation (as you indicated earlier):
Don't bring stuff you don't need. If you haven't used it over the course of one camping year, then get rid of it. Those "what if" items - are they really necessary? Will not having them create an inconvenience or a disaster? If a disaster, then keep it. Being inconvenienced isn't the most terrible thing in the world, no matter what society thinks.
Use the outdoors as extra living space. As others indicate, bring a tent when the girls want their friends to come along. Prepare salads, etc. at the picnic table.
Multi-purpose items as much as possible. Share!!!!
Use the campground facilities when possible. During the day, take a walk to the campground bathroom rather than using the RV bathroom.
Put things away after use. Using double stick tape or museum putty to hold down items that you tend to use often will eliminate the need to put it away every day. Putty down your coffee maker and make a strap to hold the carafe in. Museum putty will hold up in an earthquake, it can handle driving.
I would look at a C with a full cabover bunk. Both girls can sleep up there. Sleeping with their feet towards the cabin will add extra room for a couple friends (we used to have 8 kids laid out like that while on the road). That would allow you to get a 24ft with a dedicated bed down below for you and spouse and not have to use the dinette bed.
As another said, if you are planning on driving out for sightseeing, etc., don't hook everything up. Contrary to common believe, RVs are made to hold it until you can dump the tanks. They don't need to be hooked up to sewer in order to use the restroom or wash dishes. If you're at a full hookup facility, you can hookup the morning you will be leaving and dump - not any more work than being hooked up all the time and allows you to drive off during the stay if you desire.
Determine ahead of time what things are "risk worthy" with your outdoor gear. For me, I don't worry about my outdoor gear that much. I camp at the same places where tents camp. They leave their entire camps set up and drive away for a day, so I figure there is no reason not to leave my chairs, etc.