Came here to say the same thing as
@Mad Dog, not surprised he said it before me.
Labor Day has always proven fickle to plan around because i've both had clients and seen busy weeks at Disney/Universal on all days myself.
I would've said people tend to use the DAY itself to travel back home if they had off for the holiday and no other days attached, so i'd say that TENDS to be the least busy park day than most would initially imagine. Saturday and Sunday are a toss-up but it's best to expect anywhere from a 3-6/10 crowd level depending on which park you pick. Nothing huge. Nothing crazy. But i'd err on the side of caution with EPIC more specifically, that one is leaning 6/10 for a lot of September based purely on ticket-sales, methinks. Comparatively, the rest of UOR looks easy, breezy
(covergirl).