Melissa:
Disney allows you to make a reservation 399 days out! So you could make your reservations in almost one month's time!
As for getting all three families in the same building, Disney doesn't guarantee requests, but I do know that one of the things they consider when accommodating requests is the date you made your reservation and request. So it certainly helps you to make your reservations as early as possible! Another tidbit to know that will help you in securing your rooms close to each other is to designate your group as a "Magical Gathering." (Click
here for some more insight.)
In a nutshell, when you have more than 8 in your "party," you can enjoy the expertise of a Magical Gatherings Expert who can help you book your meals together, plan a Grand Gathering experience and generally help you plan for a larger group. From my own experience planning two large groups' trips, one piece of advice for helping you get your rooms near each other if you are making and paying for your reservations separately: make sure you ALL request the SAME room preference (preferred room vs. standard room vs. water view room). Disney works to get you as near to each other as possible, and having the same room preference increases your chances that they can make it happen!
As for waiting to see if Disney will be offering specials, my advice is to make your reservations as soon as possible so you can guarantee your dates, resort, and room preference. If a special comes along, you can always call Disney and ask for the discount or change your reservation without penalty up until 45 days out.
If you have any questions as you get closer to planning, come back to see us!
Whitney