Okay, our grand kids are 8 and 5. BUT we end up hauling just about everyone is town around a few times per week. We also do sports, BMX, dance, gymnastics, etc...and I hate having a small van. It has some room behind the back seat, the shorter ones are useless for us.
I want a full SUV. Seriously, the seats are wider so that they fit an adult hiney, not just a skinny little kid's rear, and comfortably too. They are usually made to fit a man. So when the kids are bigger they will still have leg room, shoulder room, the ability to lean back and not be on someone's lap, etc...plus if someone is a full size figure the wider more supportive seat is way better for them too.
I also want to be able to fit several bikes, all the sports equipment, flats of water and/or Gatorade, 5 gallon water jugs, all that goes with the kids as they move through their lives.
One thing I always think of when I say I want an SUV is that with a Suburban, I can set up a pack and play behind the rear seat while we're parked at an activity and the little ones can lay down and nap if it's cool enough.
It's nothing like a regular van. We have had several. All with the extra foot of space behind the rear seat. Non were extended like a Suburban is. There are so many SUV's now that I am sure you will find just what fits your lifestyle.
The one thing that I love about our current van is that the middle seat has 2 integrated car seats in it. I have never seen more than one before. This is so great for me. I don't have to move car seats or clean under them anymore. I just flip them up or down as needed.