Why not auction off a 15-passenger "Catholic Van" instead?
(We need one of those! We are currently a 2-car family, i.e., our family can no longer fit in our 2004 Yukon, which only fits 2 adults and 7 kids. So both adults have to drive on any family trips.)
P.S. Speaking of large vehicles, did you know that TRUNK SPACE/STORAGE is a huge issue for vehicles of this size? I never gave it a second thought until I had a "large family" myself. Having some trunk space for groceries, shopping bags, diaper bag, emergency supplies, luggage, Christmas gifts, etc. means you subtract at least 3 from the carrying capacity of the vehicle. So, long story short, you need a 15-passenger vehicle LONG before one would think.