You're right, it's pretty tight in a popup with a big kids in the family, and keeping things organized is a challenge!
When we camp, I'm the queen of duffle bags. Everybody only gets one, and they're color-coded by person so I immediately know whose is whose. When they're packing, I let them know how many days they need to pack for, before I plan to do the laundry. For a 10 day trip, I only do laundry once, and they need to pack 6 days worth of stuff (in case something happens and laundry gets delayed). Doing laundry only once on a trip isn't that bad to me...even that's a vacation from my normal routine, and we only have to bring half as much stuff. I do the laundry in the evening after the kids have gone to bed, so it's not cutting into my vacation time. The duffles have zip ends that can hold personal bathroom/beauty supplies, and I have a shower basket (with only one brand of shampoo/conditioner!) that whoever needs it is welcome to use.
Everybody has a place to keep their duffle bag (on the bunk ends, by where they sleep). I have separate duffles for dirty laundry and drugstore things, and each person has a little "koala" hang-up bag that they use to store personal stuff (glasses, keys, hearing aids, etc.) in the trailer. The kids get one backpack with toys/books/DS's, and dh and I take our laptop cases. Everything gets zipped into a bag or backpack when they're not using it, so there's not much searching for missing stuff. I hate having to do that!
I keep food in a laundry basket on top of a cabinet across from the galley, and that's pretty much it! The duffles get smaller as stuff gets used up and stay our of the way of the "main" part of the popup, and the laundry basket keeps food in one place and not scattered all over. Souveniers that are small enough can fit in their backpacks and bigger stuff can stay in the car until it's time to go home. We can pack the whole thing up quickly since it's pretty easy to stow the duffles and laundry basket in the car, fold up the trailer and go.
When we camp at FW, we put up our screen room with a couple of chairs. It's the only place we've ever used it! But that makes enough extra space that we haven't bothered bringing an extra tent yet, and it's a really nice place to unwind in the evenings with a glass of wine!
We've only got 3 kids (ages 6-15) so we've got one less person than your family, but I'm pretty strict about them not bringing everything they own. Most of the extras my kids would want to drag along they wouldn't use anyways, and they've really learned the value of packing light. If it doesn't fit in their duffle or backpack, it doesn't get to go. They'll be too busy at the theme parks and campground anyways, and enjoying new stuff they gotten to miss that much extra from home. We spent 16 days on the road travelling from CA to Texas, and didn't bring much more than we would have for a long weekend camping trip. It sure makes it easier not having our van packed to the gills the whole way. As long as we don't bring our dogs, it's not too bad!
Have a great trip!
Sue in Texas