This has been a DAUNTING task for a long time for me. Mini-van's are really out of the question because anybody can "settle" for that. They are not incredibly aerodynamic. We already have a Toyota Sienna anyway, and it gets about 24 MPG if I drive it "specially".
We are looking to "improve that" and try to get something much better. I wish there was a 3 cylinder Geo Metro wagon.
But a 4 cylinder with 7 passenger seating MAY be good.... but I'm having a ton of trouble finding stuff like that.