It depends on the van set up. The Aerostars my parents had (1986 and 1997) had bench seats in the second row. I could fit my son's Wizard in there and my daughter's Companion (side by side), but there was no anchor for the tether on the Wizard (have to get it retrofitted, which Ford will usually do for free). And it was a tight fit. I don't think I could have gotten a good RF install in the third row
So, we had two seven passenger vans (both year models) two captains chairs in the front, a two seater bench on the second row, and a three seater bench on the third row (no shoulder belt in the middle of the back bench).
I do recall that the 1997 Aerostar had a strange seatbelt configuration on the passenger side on the second row. Basically, if you had a car seat installed on the passenger side of the second row you couldn't get into the third row at all, without jumping through the back door. There were no head supports on the bench seats. The front captains chairs had wimpy head supports, but at least they were there.
My aunt had an Aerostar that had captains chairs in the second row and a bench in the third though, and she never really used car seats (that I remember) so I couldn't tell you how they fit.
We had the 1986 Aerostar for quite a while, most of my school age years.
We even got in a VERY bad accident in it and managed to not have severe permanent injuries (other than neck issues we'll have from whiplash, but we're alive!).
Its on a truck frame (which minivans aren't built on anymore) so it has a bit of stability when it comes to crash safety, but gas mileage may be an issue. The lady in the other car had much more "intrusion" into her car. My parents saw how it performed in that wreck and went and bought themselves another Aerostar (the '97)
I hope this made sense (I'm tired and rambling).