Working school year calendar around visitation with other parent
The background info: We have had custody of DH's 11 year old daughter since she was 3, and visitation with her mom used to be every other weekend, sometimes more often, there's no set schedule. Back in October, her mom moved off and now lives almost 5 hours away. I already had the school calendar made out, so when she was able to go to her mom's, we let her go, and if she missed "school days," we simply changed her calendar, leaving our son's the same. That worked fine, until May arrived, and he finished his year on the 13th, and she still had 3 weeks to go. (If she had finished her curriculum, I would've let her be done, too, but she was even further behind than the 3 extra weeks she was gone.)
Fast forward to now, I'm trying to figure out our schedule for next school year, working around when bio mom is able to have DSD come visit. (Both she and DS have asked they not have different breaks; neither of them liked her working when he was done.) Because her step-dad's work schedule has him in our area every three weeks, that's the only time they'll get her for a visit. This is making planning my calendar very difficult. We don't usually do "fall break" or "spring break," because we like a long break for Christmas and getting out early in the summer, but since I don't want to keep DSD from seeing her mom from start of school to Christmas, I'm going to have to plan a 3 week fall break. I like to start them back the last Monday of July, but they're going to have her from July 17-Aug 6, pushing our start date back quite a bit.
My question is, is there anyone else here who has to plan their school calendar around parental visitations, and if so, how do you do it? Even if you don't have to deal with it, do you have any advice? I think I just need some fresh perspective on it, but the way I'm feeling now, they're either going to have to have different breaks, or we're going to have to change to *official* year-round school. :(