1. What is your schools unexcused absence policy?
2. Are your kids capable of self motivation to do any work assigned for the absence and to make up any work when they return?
3. Do their current grades and behavior in school support a extended absences?
If they won't be penalized by the school, they have the fortitude to do the work, and don't have any current issues with grades and behavior I say let them miss a few days. As long as you don't make a habit of it, it won't hurt them.
If they will be punished for missing school, if you think it will set up an issue where 'they missed once it won't hurt if we do it again next semester and so on and so on', if they fight you on homework or doing assignments, or they have issues that mean a vacation will give them license to act up or feel rewared for acting up, then no, they shouldn't miss school.
Former Teacher, and Former kid who actually had a number of extended absences, but it's just my opinion.