Hiya Alma!
Welcome to planDisney! I see that you and your 'Ohana are looking to have some pool time on your upcoming holiday! Remember, 'Ohana means family. Family means nobody gets left behind or forgotten. Having gramma across the pool sure sounds disappointing but let's see how I can help.
I am not sure if you are referring to the Cabanas located poolside at a few of the Walt Disney World Resorts or the cabana-like spaces at the Water Parks. Resort
Cabanas are only available to be booked at
Disney's Contemporary Resort,
Disney's Grand Floridian Resort & Spa, and
Disney's Yacht Club Resort and Beach Club Resort. The last two Resorts share the same pool area, called
Stormalong Bay. The Cabanas are only available to be reserved for guests staying at these Resorts for the period that they are staying. These Cabanas have a maximum capacity of 6, which I did verify. Unfortunately, your family having all 7 guests above the age of 2 makes them included in the headcount. Since you are interested in reserving two cabanas know that it is not guaranteed that they will be directly next to each other. Since you have to make your reservation directly with the lovely Cast Members at Enchanting Extras at (407) WDW-PLAY, make sure to see if a note can be made with your booking. I would then follow up when you check in at your Resort. Many times, the exact Cabanas are not selected for the guest reservations till the day of to account for potential cancellations which are allowed to happen without penalty in the 24-hour window before reservation. You may get lucky with two right next to each or gramma may end up with a private Cabana while she enjoys her cocktails.
As an alternative, consider the Patios available at the water parks. I don't know if you intended to visit any of them but during your visit,
Disney's Blizzard Beach Water Park will be open and ready for all of the people in your family. While others enjoy the thrills of attractions like Summit Plummet others can enjoy the relaxation floating on the 3,000-foot-long-lazy river called
Cross Country Creek. You can then join up together in your
Polar Patio which can accommodate up to 10 guests!
Make sure to make your reservations as soon as possible as the Cabanas do book up quickly. I have heard rumors of last-minute availability the day of with half-day options but that is rare. I wish you wisdom in your decision-making. As my favorite grandmother Tala from Moana said, "The things you have learned today will guide you."(I hope)
Happy Planning!
-Nimmy