youngest is 6, we're not talking a rear-facing car seat here. Just a booster on one of the outboard seats. I concede the kids may get a little grumpy on a longer road trip, especially as they get bigger. But hey, learning to deal is part of growing up. We'll have fun and they'll remember it for the rest of their lives.
When I was a kid, we did a lot of trips in a 65 GTO and in the back of an 82 C20, under a canopy. My brother and I don't look back on our youth and complain about the lack of air conditioning, the hot vinyl seats in the GTO, or getting slobbered on by the dog in the back of the truck. We talk about all the crazy fun times we had going all over the place, camping, to the beach, blasting Def Leppard and occasionally convincing my father to "peel wheels" when no one was looking.
If a Pilot or Traverse or Sienna is your bag, that's fine by me ... some people just love comfort more than adventure. We've got other ideas in mind and places to go where those vehicles don't really make sense. So we'll put up with the complaining in order to give the kids the chance to get out there and experience the wilderness, the feeling of watching the sun rise over north Idaho knowing no one else is within miles of your campsite is worth every bit of inconvenience, in my opinion.
We may hear about the tight seating quarters some over the next few years. But 20 years from now, I can absolutely guarantee you the kids won't be talking about cramped seats in the 4Runner, they'll be looking back fondly at all those trips sleeping in a tent, hearing the wolves howl and the wind blow, watching the sunrise and sunset, seeing storms roll in over the horizon, etc.
Oh, and I've still got that GTO and it still doesn't have air conditioning. So they'll also be getting familiar with those hot vinyl seats I was talking about ...