The OM-D has very fast autofocus, as does Nikon 1 series

For kids, and anything requiring fast autofocus, the OM-D might be the better choice, it is supposed to have lightening fast autofocus. It also has very good facial detection and will focus automatically on the eyes of the subjects.

The Nikon V1 is also supposed to punch way above its weight - it is a smaller sensor than M 4/3, but there are some very favorable reviews, going much against expectations. And it has blazing autofocus.

I'd probably go with the OM-D, though, seems the best balance and most versatile!

-- Gordie