Perhaps I'm missing something here but if you are disagreeing over who will take custody of your child, then the only place to go is court as it;s obviosuly not a small matter. Wat is it exactly you are unkeen on getting in to?
Ultimately, if you want to avoid the courts then you need to thrash it with him and come to an agreement between the two of you.
I would have thought getting something legal in place would make things an awful lot easier in the long run for everyone involved. You might be able to come to a civil arrangement short term but if one of your circumstances change and someone decides they want to move away, or things get nasty or whatever, the other partner might go back on what they had previously agreed to making things very difficult for everyone and most importantly, making the child feel unsettled which I would have thought would be everyones main concern.
Good luck!