A two year stint would not be the same as home schooling for their entire school career. There are a lot of pluses to getting the kids out in the world. Travel is a great teacher. As an elementary teacher myself for 30 years, I have had concerns about some of the home schooled kids that came in to our district after four or five years at home. They often had trouble fitting in and difficulty adjusting to not having constant one to one instruction and attention. If it is found that your younger daughter is having some kind of learning problem, then you may want to keep her in a school setting where she can get the professional help that they offer.
I would also make one other suggestion. Try to decide where you will settle when this adventure is over, before you set off. That way you may be able to hook up with the local school district where the kids will wind up. They may be able to supply curricular materials so that your kids will be "instep" with their classmates when they enter the district. Many districts have their curriculums on line now, which would be beneficial for you. Core Curriculum may be out the window by the time you are ready to put down roots, so the benefit of it would not be helpful. I'm not a fan of CC, but in theory it would help people like you that may wind up on the other side of the country from you started. Good luck!