Living here for 22 years (80 miles due west of WDW), Nov can be a mixed bag. Early Nov can still be very warm but less humid. Late Nov like T-giving can be coolish (especially in the evening) and more crowded.
I would say that it depends on your kids. If they are use to wearing dresses while "playing" I'd say go for it. DH and I see lots of little ones in dresses at WDW.
If they are the type that loves the rides and such, maybe not so much as I think that some of the rides don't lend themselves to dress wearing very well. That's my opinion of course but it's what I see.
Either way, I personally still wear shorts in Nov at WDW as I just find it more practical.