We went last year from the 20th-29th. And while the beginning was busy it wasnt horribly bad until Christmas and after. Between getting to the parks for opening, using EE(AK & MK) and using FPs when possible we were able to get a lot more than we had expected done before Christmas. This freed up some time at the end of the week for us to take things slower, do some extra stuff and not fret about having to do it all.
If this were a first and only trip Id wait for a slower time, but if you think you will be going back again, with some careful planning, you should be fine.