Lisa,
I would normally recommend
Coronado Springs. I like the ambiance of the resort, and I think that it has shorter transportation times to all the parks than you get at Caribbean Beach. But with a 10 and 11 year old, you might find the amenities are better at
Caribbean Beach, if you want a lot to do at the resort. The marina seems to have more to offer, including a Pirate Cruise that is fun.
As for the pool, you might be surprised. The pools at all Disney resorts are heated (slightly) during the fall and winter months, so it may be warmer than you expect. Certainly if the weather cooperates it might be worth considering. We have swum as late at the first week of December in the past, though that is a hit-or-miss proposition.
BOTTOM LINE: If you don't expect to spend a lot of recreational time at the resort, then go with Coronado Springs. If you are planning to spend afternoons, or even a full day at your resort hotel, then go with Caribbean Beach.
Write me back if you have any follow-up questions!
Have a magical vacation!