From another thread of yours I read, you are planning on another baby, so betting a minvan/bus is definately a better option as you would have 3 children in one car and would have to get a larger car to fit 4 children in the other anyway.

A boy in my DS's class is one of 5 children and they have Ford Transit van that can seat 10 I think. It looks large but their children are older and need the room. Other alternatives are a small bus - some I've seen seat 10 and another option after that is a Kia Carnival - they can seat 8, but you lose all your storage space for prams etc.