Here are a few other options you may not have thought about:
1. One of you buy a premium annual pass. The hotel room savings runs about 30 to 40% per night which on a 5 to 7 night stay will pay for itself, especially if you are thinking about 2 rooms or a villa. You will also get 20% off merchandise if you remember to pull out your card and ask. (Regular annual pass only gives 10% off).
2. You can purchase a Tables in Wonderland card for about $75 or $80. This will allow up to 8 people eating at the same time 20% off of food purchases. It doesn't include alcohol. But when you are feeding as many people as you are, this might be a good option for you. All Disney owned sit down restaurants are included. Counter service is not included. People would have to eat together as one cannot share the card with others.
3. Landry's has a similar card which covers their restaurants. It costs $25 and the $25 is given back to you on the first visit. It covers Yak & Yeti, Trek, and Rainforest Cafe. These restaurants will give you 10% off if you have an annual pass even without their own Landry's card.
Personally, if I were in your shoes, I'd go with the cheapest option at Port Orleans Riverside. The rooms are very small, but the charm of the resort is unequaled. One can ride boats to downtown Disney, fish, swim, jog, rent Surrey bikes, and ride a horse and carriage. There will be plenty of things to do the two days you are having down time. And there are some cute gazebos for the kiddos to pretend play.
The first week in December has recently become one of the busiest weeks of the year. It seems a ton of companies have discovered it to be a good week for conventions. The second week is hit or miss depending on how many conventions are scheduled that week. January and February have less crowds, but there is more risk with the weather.
Happy planning. You can check out the DisBoards for specific questions as well.