We ALWAYS take the earliest flight into MCO and the latest flight out. Last trip our departure wasn't until 8:40! We either store our luggage or check it in with RAC (depending on which airline we're using) spend the morning at MK, doing our shopping (we ship it home) on Main St. in MK then head back to the resort to swim and spend the day. We've done this at both GF and YC with no problems. Both had great changing and showering facilities. At GF it is by the themed pool and at YC you use the health club facilities. We go in July so never had to worry about wet bathing suits - always completely dry in a few minutes but I bring a few extra ziploc bags just in case. We've always done this and it works out great for our family.
The latest check out we were ever able to get was 1:00 and there wasn't any additional charge.