If the whole purpose of this is to drive your son to school it seems to me he would be in the zone for bussing if it is too far to walk. This seems like an awful expense and hassle for the cost of a runabout stroller instead to walk to the bus stop.
That is a lot of buckling kids in and out of carseats if you have to put them in to get there, get them out to take son to his class/door/area etc, then back in for the trip home.