About a year ago, I got the Jury Duty notice. It was for the week before our vacation. The notice had a spot to put it the information about why this date wouldn't work for you AND to fill in alternate dates for which you could be available. I filled out the paperwork and sent it in promptly. About a week or two later, I got the paperwork saying that my Jury Duty had been postponed to the new date.
My understanding is that there isn't a big problem getting your dates deferred (postponed) for a valid reason (non-refundable vacation seems reasonable). But DON'T expect to go in on your Jury Duty date and get away with not serving because you have vacation the next week.
So, if your paperwork doesn't offer an option to defer, call up the Court Clerk's office and request a deferral... do this immediately so that they can plan for their jury pool needs.
ETA: I just read that you're a teacher. If you don't have any other plans, you could call the Court Clerks office and ask to be reassigned to a different date (late June or sometime in July) when they need more people for the jury pool. That way, you don't endanger your vacation and you get the whole Jury Duty thing over with. (In my case, when I called in the night before, I was one of those folks who didn't even have to show up!)