Pop Warner is a football league. Boys from age 8-15 (just a guess, i'm not so sure as the actual ages!!) play in this group. These kids come down to Orlando for their play-offs. There are also cheerleaders. And dance teams. And they stay mostly at the value and some of the moderate resorts. I didn't find that they impacted the parks very much at all. A lot of people say the kids are awful to be around in the resorts tho. However, I was there, at the AllStarMusic resort with them in '03. I didn't have a problem at all. Yes, there were kids running all over the place and girls practicing routines early in the morning. But, I requested a room on the backside of the building and I never heard any of them!!!
As to the time in Dec that they can be expected. I think there has been some discussion as to the exact time for '05. Most likely sometime within the first two weeks. I would hazard a guess as to maybe the second week. But, again....I had no problem with the kids at all and they had little impact on the parks, especially during the daytime.