They should be in school when school is in session. Teaching them that it is ok to skip school for a fun adventure is a bad idea in my way of thinking.
I supposed you think eating ice cream for dinner is a bad idea too?? Once in a while won't hurt-you just don't make a habit of it. Skipping school for a fun adventure when it's authorized by your parents is NOT the same as skipping school because you don't want to go. This is how you teach kids boundaries and decision making. And that there are consequences to your actions. In my son's case there were two consequences-one was a VERY enjoyable, stress-relieving vacation. The second was some extra work. Rigid items break. Flexible ones bend. Life is about flexibility, choices and repercussions.