Forget the Outback version as you have kids and you're not going too far off the beaten track now and what's more your water won't last more than about 4 days with frugal sponge baths, etc and with a 90L fridge and 5 mouths to feed you won't want to be away from the shops too long anyway.
Our 2003 road Dove and Suzuki SX4 did close to 15000km up the NW of WA and we've been on plenty of corrugated and dirt tracks Jayco wouldn't exactly approve of. You'll need to bracket the cupboard shelves for corrugated roads-
http://www.myswag.org/index.php?topic=29589.msg461924#msg461924but as for sealing Jaycos there's the door and fridge venting and open flyscreens when you're camped so campers aren't dustproof anymore than home is with the windows open. Like all caras pay attention to seam sealing for water egress and don't assume factory production lines have got it all 100% all the time.
The Dove layout gives you the best bench space with table/lounge near the door so kids come in and sit down there without disturbing cookie. Now the table will seat 4 so that's the 2 littleys near the wall, the eldest alongside at the back and cookie alongside the other littley closest the kitchen and dad perhaps with a lap stable table on the lounge. With 3 kids that's one sex or 2 so same 2 go on the double, mum and dad on the queen and eldest on the table dropdown so get the plugin bedlights so mum and dad can have the light on in bed (get 48 LED 5050 panels all round instead of the hot globes) with the curtains drawn. They're like 3 separate rooms and you need a big heavy van to duplicate that layout.
Now you want a Fiamma awning with alum director chairs with side tables and perhaps a table for outside and I'd hold off on the annexe and see how you go without one (perhaps tee up a hot price with dealer should you want to add one on the far side later) So many annexes are like new in the bag as you're not likely to set it up unless staying for a few days, although they are handy with kids on wet days.
Don't worry about the fridge not opposite the door as flicking the roof catches and winding the roof up just enough to allow the door to clear allows the kids access and they love to jump in the cubby to get tucker and gear out for lunch, etc (you'll have to have a roster to avoid sibling rivalry)
Why Jayco windups? Just look around you on the road and in the parks and remember fuel won't get any cheaper and it's wind resistance on our big flat continent that affects that the most. I reckon ULP would be around $2.40/L at William Creek at present and we paid $2.09 up the NW before the latest rise.
