This is another shot from yesterday, the dull background was too prominent so I tired some new things I've picked up from reading this book
After raw processing, copied the background layer, filter -> Lens Blur, created a layer mask, selected large soft brush with default black and painted over the kids and foreground on my layer mask @ 100% opacity then a few lower opacity brush strokes higher to make the blur fade in .... took 2 minutes :)
You did a really nice job with blurring the background - I always seem to get too picky with it but this looks great. And they look like they're having a blast!