Hi Marcie,
All of the swimming pools at Port Orleans (and all of the Disney resorts) are outdoors. The good news is that they are heated, year-round to a comfortable temperature, so bring along bathing suits for your kids! As for whether your family will think it is warm enough to swim, the answer is, it depends on your personal preferences and the weather during your trip. I have travelled to Disney in January when it was unseasonably warm (and we were in the pool every day), average (in which case we went to the pool several times during the afternoon, when the sun was high) and unusually cold (in which case, we skipped the pool and spent more time at the parks). I do suggest bringing along a thick bath robe, towel or other cover-up to help your kids warm up after swimming.
No matter what time of year you visit, you will generally find people enjoying the pools at Walt Disney World. In fact, I just returned from a December trip during a real cold-spell. Nevertheless, the pool at my resort was packed with kids (and a few brave adults) having a blast! My two boys were among them!
Have a magical trip!
Tanya