What a great idea. And brilliantly executed too. Considering how kids usually do exactly the opposite of what the photographer wants, i'd say you've done very well indeed.
Fantasic shots. You can tell how much the kids enjoyed it.
I too do something similar when the young ones start to get distracted. We take a few mintues and I show them the camera's, how to look in the viewfinder and push the shutter button. We point at mom and day or siblings and after they take a few snaps we look at them and then oohhh and aahhhh over them together without anyone else being able to see. It's their special reward for hanging in there when they are tired or bored and it makes them so proud.
I find that doing this also helps them stay focused knowing they can take more pictures later if they try to co-operate (it's the effort I'm after at that age).
I also make a point to put their pictures on the DVD even if they are blury as I present family sessions as an experience, not just pictures. Besides, I LOVE working with kids and the way they light up when they get to hold the cool equipment is a really great moment
! Great set up! Way to hook us in and smack us with cuteness! 
