Generally speaking the earler week would be a little better. Really both should be fine. The closer it gets to Christmas, the more crowded it becomes. But it shouldn't be getting too crowded by the 15th.
I don't think you will notice the Pop Warner thing unless you are staying at the same hotel - usually an All-Star or moderate.
We were at All-Star sports once during a cheerleading competition and at Dixie Landings when a lot of the Pop Warner people were there. But it was not a problem. The parks were still very uncrowded. We saw the teams and stuff, but it didn't overwhelm the resort (Dixie Landings). I am sure that is because DL is so spread out (DL = POR now).
The cheerleaders were everywhere at ASSports, but they were checking out and they were all gathered in the main hall.
I think you will be happy with either - just avoid MK on Saturday.
As for Dumbo. It depends on the size of the adult and the kids. Toddlers with a normal size adult should be fine. Bigger kids or a bigger adult - probably not. How young are your kids?