Here where I live its not a hassle taking your child out of school for a few days( unless of course its exam time , in which case that would be stupid) so we just tell the school ,, not a big deal at all. I have heard it is more difficult in States because schools are sometimes finacially penalized if they have bad attendence.. so they make really strict rules. My feeling is, from my own experiences( 3 kids) is that once kids are in high school I would not remove them for more then a few days.. as the semester system means if they miss 3 days they are missing 6 days of work really... enough for most kids to have to keep up on. For kids under 12 I have taken kids out for as long as 10 days with no difference in their marks( actually one child did BETTER doing his work one on one with me anyways.. got more done then in school. LOL )
Hopefully, if your child is a decent student to begin with,, and not in the later years at high school, then you won't get too much hassle over missing a few days( that sounds so silly,, )
I would also go online, and see what the curriculum for your childs school year is,, and see if you can tie trip in with that,, in our school system they do revolutions( French, Industrial, American etc) in grade 8 or 19,, Rome and Anicent civilizations in grade 9 or 10,, etc etc.. that way maybe you could actually plan trip around what they will be covering this year,, seems smart to me to make the holiday a real learning experience that will aid child at exam time!
Good luck,, and hopefully your child is not too old to make this viable, as I said,, I would be hesitant if child is older then grade 8 or 9..