I think fullsize is a little too big for trails, but with almost any expo rig besides a suburban or fullsize truck, you won't be sleeping in the back, especially with the kids. Even in an 80series landcruiser it will be tough to sleep two if you have tons of gear, however a roof top tent is always an option (a very
option). For me I think the disadvantages outweigh the benefits for an RTT, but lots of people use them and love them. I think the decently priced mombasa rtt would fit the whole family just fine.
Options I would consider:
60 series Landcruiser - cheap, awesome looking, tough, slow, poor mileage, reliable, old, 60s had carb and 5 speed, 62s had efi and auto.
80 series Landcruiser - beefy, lots of room, comfy, coil springs, full floating axles, factory lockers option, slow, auto tranny, poor mileage, reliable, not too big on the trail
100 series landcruiser - beefy, v8, toughest ifs there is, factory rear locker option, lots of room, heavy and bulky, maybe a little TOO nice, may be expensive depending on year
4 door taco - fast, decent mileage, ifs, rear locker option, reliable, expensive
Unless you are really into Landrovers, stay away from them. I'd take a XJ before I took a rover. XJs probably are a decent option too, lots of people use them, but they aren't as :greg: as toyotas.
The cheaper the vehicle you buy, the more you can spend on sweet gear. If you buy a rig thats already set up, it will be much much cheaper. I bought my 97 Lexus (80 series) for just over $9k and it already had factory lockers, 2.5" lift (the perfect size for expo IMO), 33" tires, sliders, front and rear bumpers, and a roof rack. To get it how I want it will only take a few grand more (swing out, 4.88s, snorkel).