We have gone to WDW the week leading up to and through Labour Day since 2012 (your dates fall within that range). We fly down the Saturday before the labour day weekend and fly back on labour day Monday. Last year Irma hit after those dates. We flew home on the Labour Day monday and I believe Irma started to be an issue at the end of that week Thursday/Friday.
I recall one year a hurricane was hitting the keys exactly the time of our flight. All southern Florida airports were shut down, but Orlando was still open. That was the closest call we’ve come in our 6 trips. Every year I watch the national hurricane centre starting about 2 weeks before departure up until we are leaving just to see if I need to make a last minute change, so far so good (knock on wood).
It is right in the middle of hurricane season though, so the risk is there. Weather in general is typical Florida summer, super hot, super humid and you can almost set your watch by the mid afternoon downpours/thunderstorms.