Daxx's Wife here. I'm a Kindergarten teacher and a mom of an 8 yo DS. So, what I have to say comes to you as a parent and an educator.
I am pulling DS out for 2 days of school later this week for a WDW vaca. I know that 2 days is not unreasonable esp. at this point in the school year. Things are winding down, starting to wrap up loose ends and I don't expect him to miss a lot w/being out for 2 days. As you can tell, I am all for taking students out of school for vacations.
However, regardless of how well DS performs in school, I would not consider pulling him out for 2 weeks esp. in the beginning of the school year. Regardless of what grade he's going into. The first month of school is an important time when routines are being established, new concepts are being introduced and teachers are gearing students up for the "long haul" -- esp. in 5th grade. In my school, Kindergarteners are working hard the first month of school. It's not a slow adaptation and fun and games ... it is when we begin a lot of core learning and when I determine how to group my students based on their skills. You have to remember that Kdg. isn't all just cut, paste, color and play anymore. To miss two weeks in the first month is missing a lot.
While you can do the work at home, you will miss out on materials learned w/in the classroom. Things taught that don't show up on homework. And, yes ... in my Kindergarten, my students get homework every night -- whether it relates to printing, reading, phonics or math.
I'd rethink the two weeks in Sept. and move it out closer to the holidays (ie: Christmas) when things in school tend to become a bit less intense b/c teachers don't want to introduce new concepts until kids are back from winter break.
Food for thought ... you need to know your school's absence policy and their take on missed time due to illegal absences (non-illness).