Amy,
Relax, my 'sisters' and I are here to help!
I think that if you can get your big picture planning (resort, airfare, etc.) planned at least 7 months out, that would be great. That way, when you can start making dining reservations 6-months out, you are already set. BUT, if you are already inside of this window, don't fret! That is just a general rule to follow if you can.
So if you know when you are planning on coming, you have an initial planning window. From there you can consider a few other steps;
- Keep asking this panel questions about your plans, so that you get a fellow parent's perspective
- Consider booking through a Disney-authorized, no-fee agency who can help you with a lot of the planning (MouseFan Travel is a great example)
- Look at some of the Disney enthusiast sites (like AllEars Dot Net and the DIS Boards), and listen to podcasts (WDW Radio, WDW Today, and the DIS Podcast all come to mind) if you feel like getting more into the planning. These are not a must, but for some are a fun way to get added ideas and tips.
And write me back directly from my bio page to ask specific questions. We can discuss one question at a time things like; time to visit, how to book, what parks to go to on what day, where to eat, how to save money, etc.
Have a magical vacation!