Hi Sarah,
What a wonderful and generous Dad you have!
Without knowing the make up of the individual families, I will make some general statements and if you would like more information, you can ask a follow up question.
You will need one person to book all of your reservations. This will help make your request to be next to one another more likely to happen. Remember you can only make a request to have rooms next to one another but is it not a guarantee. This is why I would recommend getting two rooms as it increases the chance your are next too or across the hall from each other.
One option is to stay at a
villa. You could book deluxe villa for eight and then a studio for four. The room with eight would have a full kitchen, extra bath and washer/dryer unit. The studio would have a kitchenette. Having at least breakfast in your rooms, could save enough to justify the upgrade in room. Plus if you add in the snacks, beverages and another meal, it could be a nice way to go. You can order groceries from an online grocer such as GardenGrocer.com to stock your fridge.
The other option is booking two family suites at either Art of Animation or All-Star Music. Each room would sleep six and have two full bathrooms and a kitchenette.
Wishing you a magical vacation!
Beth