The first week in November should still have some F&W activities. I think the weather would be nicer then as well. I've been to Orlando Florida in March, and in November, and I've had better luck with nice weather in November, so that would be my choice!
But if you have to pick just one, and can wait until November, I would pick November. The weather will still be great, kids are in school. But in March, that is spring break time, so the crowds would probably be a little more than the beginning of November. That's what I would believe.