I hope you are keeping your trip a secret from everyone in the extended family right now. You don't want it getting back to your WH and him just booking his own trip to the same resort. Your kids are all adults. No one has to report to him about anything. Just don't tell him.
If you've already told them general information do not share what resort so no one can fly down and just show up. Maybe call the resort and ask if you can put a confidential name on the reservation as you are dealing with a stalker and don't want him calling around trying to figure out what resort you are staying at.
Inform the children not to tell.
If this is all disclosed already, perhaps tell the extended family that your resort called you and was having some kind of issue and asked if you would mind being bumped you up to their much nicer sister property down the road 40 miles. Do your research and come up with a name of another nicer more expensive resort and just leave it out there - if he shows up...he'll be paying through the teeth to stay somewhere besides your resort and if he stops by your resort you can instantly have him removed as a non-guest harassing you and your family.
Never underestimate the entitlement of a wayward spouse. He probably won't show up choosing to stay behind and brood the victim to his disinterested family (who are stuck with him).
Have you communicated with him that you are going dark, why and when, if ever, you will speak or see him again? Have you found an intermediary to act as a communication filter between you and your wayward husband? It should be a person committed to protecting you from all drama and impertinent commentary, discussion, upset relating to your wayward husband?
Have you turned off the iCloud monitoring? It's how you discovered the new OW which is terrific information (it confirms that this wasn't about you - but it never really was in the first place and monitoring him just keeps you engaged in craziness). Let someone else access it and read for essential legal information but have them change the password or whatever it takes such that you won't even be tempted or able to access yourself in any weak moment.
Nice creative thinking about Christmas. Being dark and protected is possible with a little work.
The internet is 90% complaining and entitlement and I hate it because I deserve better!
