I change the rfing seats between vehicles. (We have 4 rfing seats, but I play musical car seats all the time.) Currently the seats are rfing avenue, rfing scenera, and a turbobooster. The turbo kid has some issues with buckling, but is usually okay. She's next to the window and tends to hang her head way down when asleep. I have this idea of getting her a seat with great sip, but I fear it won't fit- or if it does it will be barely.
Recently we had the nautilus in the middle with boosters on the sides. It was awful how much crying and screaming took place while I had to do the trick with moving the seat, buckling, then sticking the seat into place.
We are planning to get a Sienna in about 6 months. Then we could put the booster kiddos in the middle. Or, one in the middle with the fp and one on the side. Not sure we could fit with something with sip.
I know those rfing seats that are up on bases free up space to buckle, but there is no way I could convince dh to shell out that kind of money for seats that might fit in the van- plus, the little ones are really little and will likely be 40 pounds by age 7.
Oh, and the bench is 50 inches long. There is a 2-seater bench with more room, but If I buy one booster with good sip, I want it to be the one by the window. The child who sits in the middlish position sleeps beautifully in her turbo and is not near a window.