Thanks, all! Perhaps I'll bring a slightly more 'dressy' set of clothes for us, stash them in a locker at MK, and do a quick change before heading over. I'm not going to stress over it, though. We don't usually wear our swimsuits to the parks anyway-we have very Irish skin-so probably whatever we have on at the time will be fine.
Lindsay-thanks for the suggestion of a light sweater. We're heading down in August, so you know the A/C will be blasting!
I appreciate the info, everyone!