Hi Mark,
I love Disney in August as you can enjoy everything the Walt Disney World Resorts have to offer! For me, it means not freezing in the pools and enjoying the water parks.
Your group is staying at two great locations.
Disney's Animal Kingdom Lodge is unique in its design. You feel like you are on safari and the animals on property add to the authenticity. Two of my favorite restaurants, Boma and Jiko are on-site and I highly recommend trying one or both. Plus check out the resort at night by looking at the animals with night vision goggles.
Disney's Saratoga Springs & Resort is a great location to head to Downtown Disney for shopping, dining or other entertainment. You can either walk or take a book to this fun location.
With everyone having cell phones, I never thought about using a phone to call another room at a different resort. However, for international guests or guests with limited cell phone plans, I could see why this would be useful. Speaking directly with Disney on this question, it would be free as it would be considered a local call. But the easy thing to do is call the operator at the resort and have them connect you.
Wishing you a magical vacation!
Beth