I'm a wagon fan myself, although more on the compact side than what it sounds like you are interested in. My first (and only) thought was the "not-quite-a-minivan" Mazda5. I don't know what else would have the type of seating you're interested in outside of a minivan or maybe larger SUVs. I'm not sure they offer full leather though.
The wagons I like (A4, 328xi, V50, Jetta) are all small. We have only 1 child (11) plus a big dog (Bernese Mt Dog) and my '07 A4 is tight. I wouldn't want a teenager behind me (6' 0") in the rear seat for a long haul. In a larger size wagon I think you'd end up with a traditional rear seat and your options there are the usual european suspects, Volvo, A6, BMW 5(my father in law loves his V70 with 150K+ miles that he bought used at >100K). There was another wagon post here where the Dodge Magnum was suggested as well.