Rather than a number of days or vague phrasing like “this week,” giving exact dates helps prevent confusion and lets senders know when they can expect a response from you.
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.

If the person keeps you on the message thread in which they then contact someone else (ideally, the person you stated in your out of office message as the one who’s handling urgent issues in your absence), you are literally kept in the loop and can see for yourself that all was handled when you get back. Of course, this works even better if you check the most recent items in your inbox first when you get back.
Honest communication, even in the form of an email auto reply, is a roadmap. It helps people understand how best to help you and, in turn, allows them to better help themselves. Straightforward expectation setting is a way to be respectful of your coworkers’ time and pressures, but most importantly, it’s a way to be respectful of and guard your time. Even if you don’t feel an intense need to be more open in your workplace correspondence, consider modeling the behavior for others who work with you or, especially, those who work for you. It’s a small change in behavior but it’s a meaningful one. And this summer is the perfect time to start.