You may also want to include bullet points of what is in progress so that your client knows you’re on top of things. That will also likely reduce the amount of emails sitting in your inbox when you return. Unlike a more generalized email (like the one I’ve provided) that you can send en masse, you’ll want to set aside some time to send more personalized emails out.
Website: https://www.wordexceltemplates.com/office-closed-for-holidays-email-template/

I worked with a guy years ago who would update his voicemail greeting literally every time he left the office. So the bare minimum would be that he’d record a new message when he arrived in the office in the morning. Then, when leaving for lunch he’d record a new greeting listing the time he would be back in the office, then he’d record a new message when he got back from lunch, then a new one at the end of the day saying he would be back in the morning. That’s not even counting the times he was out of the office on work business. It was deranged, especially since he had the type of job where he would normally be in and out of the office often.
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.