I usually put my boss in my OOO, because if something is so urgent that it needs to be delegated RIGHT NOW then it’s urgent enough that my boss should know about it, and he’s also in the best position to know who on the team to delegate it to based on everyone’s workloads and what can be dropped. But the most likely result is that whoever is emailing me either waits for me to get back because it’s not that urgent or goes to the next/backup person based on our central documentation about who to contact for particular issues.
If you need assistance during this time, one of my team members will be able to help. They can be contacted at [phone number] Monday-Friday from 8-5.

Then, all that’s left to do is turn it on before you abandon your desk, and get prepared for a relaxing holiday break—without feeling the need to be constantly tethered to your inbox.
Seconded, with one exception: I got one once from a distant coworker which said “I have broken my arm in a kitten-related fall and will be out for (…)”. Everyone else uses boilerplate language so that one definitely stood out, but I thought it was the right level of mildly amusing.