Howdy Kim!
We stayed in a Grand Villa at
Disney's Saratoga Springs Resort & Spa a few years ago and it was an amazing experience. The Grand Villas are spacious and beautiful and I know you will enjoy every minute.
I just spoke with a Cast Member at Saratoga Springs and you can request a roll away bed if your son doesn't want to sleep on the queen-size sleeper sofa. There is a $15 + tax per night fee for the use of the roll away bed.
You can request the roll away bed prior to your arrival by contacting Disney Vacation Club Member Services (or wherever you made your reservation) or you can make the request with the front desk at the resort when you arrive.
I don't know if you have ever slept on the sleeper sofas at Walt Disney World Resort but they are actually rather comfortable. You might test them out before you request the roll away.
I'm so excited for you. I know you are going to love your time at Saratoga Springs. I'm so glad your son will be joining you for part of your vacation. You will have plenty of room in the Grand Villa and I know it will be a magical vacation for all!!
Thanks so much for your question and please let me know if you need any further information. Have a magical day!