We've gone that week for the past two years and, while it isn't the lowest crowd time (by far!), it's definitely manageable. I will say, though, we are not park-commandos and we never spend entire days in the parks. We typically do half-days with other activities scheduled to fill in the other half. Last year, in addition to the parks we did The Void at DS followed by touring the holiday offerings there plus dinner at Cali Grill, a pool/spa day followed by HDDR and a private sleigh ride through Ft. W. We also did
MVMCP (MK will be significantly less crowded on party days) and the Star Wars fireworks dessert party. We also made sure to book the more hard-to-get FP+ at our 60 day mark. My biggest advice would be to avoid MK on a non-party day, however, if you want to see HEA, you'll need to at least go in the evening. If you do, consider an HEA dessert party. Crowds got significantly bigger as the week went on. We left the Saturday morning before Christmas last year and our resort (WL) was packed with people arriving the Friday evening before.
My DH is not a big WDW fan, but, I've found, if I mix park touring in with things I know he will like - good meals, some pool time, upcharge events in the parks to avoid crowds - it becomes a great vacation for everyone.