Next summer is probably going to be as busy as a holida
I went to DLR in mid August last year and the weather was perfect - I think i wore capri pants and didn't feel hot at all so it can be hit or miss. From what i've read, on average the summertime weather of DLR is more comfortable than WDW.I would go in late August, stay maybe a couple of days longer (which may be possible as prices are lower than Christmas/Easter and you have more vacation days to work with), and avoid the heat of the day. Go to the parks right at opening, do rides etc. until 11 or so, maybe visit a restaurant or some longer indoor stuff as it gets hotter. Return to hotel/pool/waterpark and then go back to the parks in the early evening. Even with less hours you will get more done than during the really busy times.
We have been to both DLR and WDW in August before and for me, WDW is fine but I won't do DLR again in the summer heat. I think mostly because we only have three days in DLR and so it seems a waste to spend only half the day at the parks. So we try to power through and it is miserable (I also do better with humidity than dry heat but that is rather unusual, I think).


