We just got back from WDW Tuesday and as far as the fires go its will depend on the wind. We had times when the wind would shift and the smoke was very bad, then a wind shift and you coulld not tell there was a fire anywhere to be found. The bus Driver told us the fire is a swamp fire and is burning down into the ground which is the reason for the thick smoke. They have burned down about 4' but can go as deep as 20', The fire itself should not give you any problems but the smoke may be a prob for some peaple.
Have A Disney Day