I guess I will be the odd man out and be the only voice of opposition here.....
I don't think it's a really good idea. My kids are 11, 9 and 5. I feel very strongly that I want to show them what Amereica has to offer and I want to travel with them. Our jobs really limit the length of time we are permitted to take off and how far we can travel. But even if we were rich and never had to work again, I would take trips on school breaks. We have several breaks during the year and the entire summer to consider.
There is value in traveling but there is also value in having roots and staying put. There are many activities that are also important to kids that can't happen with constant travel. How about scouts, athletic teams, etc? You can do these things even if you homeschool but not if you are constantly traveling. Travel is a great way to educate kids but I feel your kids would be missing out on a lot of things that can't be found by moving so much. And friends aren't only important in highschool, they are also important to gradeschoolers. Your daughter that struggles with math may very well always struggle with math and being out of the system for 2 years may be more of a disservice for her than you realize. Two years of travel is a VERY long time for kids. Maybe do 3 months in the summer, 2 weeks at Christmas and a week at spring break. Sounds like the best of both worlds to me.