If the ceiling is too high, sometimes I will use a second flash set up on a bookshelf or nearby table for a key. I find that with this set up, a bounce card on the flash works well.
Another technique that I add to the mix is bouncing the flash off the wall, but I usually switch to wall bouncing only when the subject is playing next to said wall. Hallways work wonders for bouncing light around.
The only issue that you will encounter with this idea is the color of the walls. Make sure that you use a gray card to set your white balance in each set up that you do.
One of the reasons that I go with TTL in these situations is the the children tend to move at the speed of light, and more often than not you will only have one chance to capture whatever they are doing. Having lighting set up in the most versatile way possible and letting your subject do what they do in their home environment will give you great results.