between xmas and NY or after NY??

Both times are bad. After NY the majority of snowbirders will be leaving. Between Christmas and New Years you'll have the complete population traveling.

Would you consider driving the RV south (it doesn't have to be to your final destination) but just until you can kind of count on the weather, stay there, in a new area to explore, then winterize it if necessary and drive only your truck or car back for Christmas?

Another option is go to your destination early and fly back. Have the kids give you the trip as your Christmas gift. :)

Being from Michigan we used to get to our destination of Gulf Shores, Alabama early in Oct/Nov and then just drive back for the holidays. It worked for us.

Good luck!

I would just go when weather is OK, as that time of year the last thing you want is to be driving in a storm.