Ok, here is the scoop. Of course I would never ask my children to do something like this - it's a composite that tried to achieve a certain level of verisimilitude. I had the camera on a tripod and I first took an image of the scene without the children. I had to use a long exposure to capture the weak ambient (tungsten in the living room and fluorescent in the kitchen) - I ended up doing an f/10 1/2 sec exposure for my image canvas. The additional light was a big WL3200 strobe pointed to the wall behind the camera filling the place with diffused light. The strobe had a full cut CTO gel on it to mesh with the available ambient, which wasn't much. I kept the same lighting and exposure for the three exposures that took to create the final image. I ended up with ambient contributing 20% of the light you see and strobe giving the other 80%. Because flourescent light rendered green with the camera set to Tungsten, I had to do some color correction in the kitchen to keep it looking natural.
The trick to make them look real was to let them climb a ladder and (carefully) ask them to pose as if they were falling, facial expression included. Then I removed the ladder in postprocessing. The children were exactly in the position you see them when I capture their frames, so it was a simple matter to selecting out and eliminating the space around them with the ladder metal. Simple but a bit time consuming. There are problems with the image because this was just for fun and not a highly planned effort - my daughter's hair should be flying a little more, one shoe should be in the air for more interest, and I am not sure the motion blur is good enough. But the important thing for me was the planning and the time I spent with them creating this imaginary scene.
All the credit goes to my children for thinking up the idea and being willing, patient collaborators. They got a small gift in exchange.
Thanks for all the comments!