All very good responses. If you haven't already, you'll need to budget a used pitching machine, decent catcher's gear, game balls and practice balls, throw-down bases, and a portable hitting net is not a bad idea either.
But the most important element is one that's been mentioned already a number of times, communication. Have a very thorough parent meeting at the very beginning. I prepared a document that spelled out what their expectations should be and what mine are; from participation to fundraising to behavior at the ballpark. I wrote it in a manner that was not threatening but certainly not vague. Then, I had them sign it and gave them a copy. It even spelled out how we would handle the removal of a player from the team. As far as the assistant coaches and your manager, I brought them aboard after explaining to them what their specific roles would be, so there would be no misunderstanding. It sounds rather tough but it was not presented that way. It definitely helped us avoid complications that many other travel teams deal with routinely.
Is it possible to get a copy of the document you created? Don't want to recreate the wheel when there is one that rolls.