Do run the NPC with the scenarios as @ucbalumnus suggests. However. also talk to the college financial aid officers as to how they handle halved EFCs when a second child goes to college while that first one is still at their school. Surprisingly, the answer to this is not what I’d have accepted. Many schools will take that second child into account in giving that initial financial aid package, but are not so fast in changing that package one they have that student.