Re: Was it hard for you to find a 12-15 passenger van?
I can understand! We have six kids ages 7 months to 12 years and we really struggled with finding a vehicle that would fit everyone. We considered a 12 passenger van but with the price of the van and the increased gas cost, we knew that it would be pricey. (Also, I think I would have a hard time being comfortable with driving a large van, especially when it comes to parking in underground parking garages at museums, etc.)
We thought we should get a used Honda Odyssey or Toyota Sienna (8 passenger). However, we were shocked at how much they sold for used. Much like you, I lamented our predicament on another site and another mom mentioned to me what they did, which is then what we did, saving us thousands. We bought a Chrysler Town and Country (same thing as a Dodge Grand Caravan) and removed the two person bench seat, replacing it with a three person bench seat. (My parents didn't want their three person seat, so they gave it to us--otherwise, they can be found at a junkyard.) The floor mounting brackets in the middle row accomodate either a two person or three person bench seat. We now have an eight passenger minivan, and it works out great for us! My 5 year old is in a five point harness in the middle back with my two older boys on either side. Then on the other bench seat, we have my rf two year old, my 7 year old in a five point harness, and my rf baby in an infant seat. My kids are petite, so they fit in harnesses for a long time, which helps to deal with the fact that there are only four shoulder belts. Then I can use the lap belts for car seats. Sunshine Radians are nice narrow seats, which definitely helps with this arrangement.
The kids are able to slide into the back quite easily. I was concerned there wouldn't be enough room, but it's totally fine. (I actually like it much better than our other van which still has the normal bucket seats and the kids have to go in between them down the middle "aisle" of the van to get to the back.
We realize it won't work forever. I imagine as our kids get older and bigger, it will get more crunched, and if we go camping or traveling for more than a couple days we use a cartop luggage carrier to carry the extra "stuff." But for now it works great and is an option that we could afford. Hopefully in a few more years we can get something a bit bigger.