I wouldn't worry about their being in different schools -- they are young and will adapt if nobody gives them any reason not to.
We moved when I was six, right before I started school, and my brother stayed in the other school district. I never thought about it at all until just recently when we started looking at houses and talking about the possibility of driving the kids to a bus stop to keep them in the district we're in now, and I realized that my dad drove my brother about 4 miles every day to catch the other district's bus, while I caught the bus that stopped in front of our house! He was in high school, so we wouldn't have been in the same place anyway.
Ironically, the school that my brother stayed in is the one we're trying to keep our kids in now.
