70-200 first, especially if it's your first lens this in focal length range. Most people already have a midrange zoom/prime, so the 24-70 is more often a smaller upgrade than the 70-200 is. The 70-200 is great when kids are running outside and for sports (i.e. soccer), when the kids get older. If you don't have one already, use a strap (i.e. BlackRapid)/harness system, which makes it much more comfortable to lug around.
The 24-70 looks to be an excellent lens but f/2.8 is sometimes not fast enough for indoor ambient photography, where faster primes are more useful. Plus, you'd be paying an early-adoption premium for getting the 24-70 II now.