Welcome to the madness!
-All I can say is they really fill up fast!
-Buy a trailer 2 feet longer than you think you need...(just do it.)
-Consider making sure the tallest one of you can stand up in it, otherwise keep the tent.
-Pay the extra to have an RV style door installed at the factory. Thank us later.
-Same for two windows; high and offset (one front, other rear on the other side for crossflow, thanks "Gonefishin".
-Do you plan to haul any gear or toys? (bikes, boats, etc?)
-Those kids grow fast, don't wait, my two youngest nearing exit from high school, "it was only yesterday we were camping at..." and as they grew, they needed more space and room for a friend from time to time.
I too wanted a rear galley, but quickly realized it interfered with loading/unloading gear. I was going to build a folding roof over the barn doors, but in my case, the top of the doors are really too high from the ground to make easy use of. I went standard leaf spring axles for better ground clearance.
I took pictures of our tent camping outings to see what we took and how we used it. We never cooked inside, unless the weather was terrible, so the outside galley setup stayed.
I like your layout ideas, but if you are considering a cargo for your base, it makes the build go much faster and stronger.
Checkout these for additional ideas:
Ours (sleeps 6):
http://www.tnttt.com/viewtopic.php?f=42&t=48345PA Wilds 7x16 (outsidezion):
http://www.tnttt.com/viewtopic.php?f=42&t=61833WA 7X12 single axle-simple, functional, yes even cute.
http://www.tnttt.com/viewtopic.php?t=40504Gonefishin 6x12: another all-time favorite, but where would your kids sleep in this 6x12? (did I say that out out loud?)
http://www.tnttt.com/viewtopic.php?t=33924Trailer for 4 please:
http://www.tnttt.com/viewtopic.php?f=42&t=65019BTW, what is your tow vehicle, vs trailer loaded weight, and do you have any plans for light off road use?
Idea farm here: I think, If I had a 4WD tow rig, one of those Cargo Craft off-road styled trailers modified for my use would be the ticket today. They weren't building them when I designed mine.
http://www.tnttt.com/viewtopic.php?f=42&t=65926Garage door discussions:
http://www.tnttt.com/viewtopic.php?f=42&t=60903Oh, two more ideas, clear out your garage floor, set up your trailer layout on the floor, blue tape, etc, see how multiple ideas work, or don't. Have the family enter/exit the layout as if the trailer was there.
Once you get the trailer, make a few dry runs before the final build out, you'll be amazed at how the design will change, once you start camping out of it.
Best,
David