Bi-state custody is a big pain. And it's hard on the kids for a parent to be so far away. If you are still on amicable terms, see if you can reason him out of it. You should get a lawyer or see if the court can tell you where to get free legal advise - for both of you if you're working together on this. If you really agree on everything, you could share a lawyer and split the cost of having him/her draw up the documents to get it done.
In my experience, a judge won't let small children be separate from their primary caregiver for a long period of time for visitation (especially if you're breast-feeding), but once they get older, they might be able to do weeks or months at a time with the second parent. If you take a stand on it, you might not have to do any extra driving to accomodate him, but you can offer to drive them to see him. The way I see it, he is making a choice to move away from his kids, and he should take the time out of his schedule to travel to see them. I think in most places (if not everywhere) you must live separately for 6 months to get a divorce or you must agree in writing to waive the 6 month waiting period.