With the Uplander, you have two rear seats that fold down separately.
We also had 3 adults, 2 children 7 & 9. One adult sat in very back and children in middle. Your carseats would fit in middle. The big thing is how much luggage you will have. If you don't think this will work, I'd go for full size van. Trailblazer would definitely not work as I have driven one of these too.
Another thought: Go to car dealership and look at the Uplander, then you'll know for sure.