Hi there Pat!
Wow, a Grand Gathering for 17 people! Nine whole days of family fun, I am so excited for you!
I can tell you are a master planner...and your planning will make this magical for everyone. The parks calendars are put on
www.disneyworld.com about 6 months in advance; they should be up soon for September. October will be up (at the latest) within a month after that. Keep on eye on these links to find out when the parades, fireworks and extra magic hours will be:
Magic Kingdom
Epcot
Disney's Hollywood Studios
Animal Kingdom
Note too that if you want to make advanced dining reservations(ADRs), these can be made 180 days (6 months) in advance...so that would be approximately March 24th (I say approximately...call 1-407-WDW-DINE and they will tell you the
exact date you can make reservations). I strongly suggest you call at 7am on the 180th day to give yourself the best chance of getting those special reservations.
Pat, I hope this helps. Write back if you have any more questions!