Since my son was in preschool, we had taken him out of school for two weeks in october. He is now in grade three and we have separated it down to 7 school days in Oct and 3 school days in march (since he has a week for spring break).
I think if you speak to the teacher and see what they think, it would help you in your decision. It also depends on how quickly they can catch up. In Kindergarten, my son took maybe a day or two to catch up. There wasn't much new they did and we always work with him at home. On our last trip, at grade 3, he missed 7 days of school and he took a few days to catch up also.
I believe it really depends on your child and how they will be able to cope coming back.