LOl at some comments on this thread - again!
Why does owning a games console mean that all other forms of playing and interaction suddenly stops and goes out of the window?
Are your children incapable of being able to swap between activities and to spend their days doing a variety of activities, sometimes playing alone and sometimes with others?
Because my DD can and does. Yes, she has a DS which she plays on and off. But she also plays in lots of other ways too - reading, writing, drawing, trampoline, playing outside, playing with Barbie and Polly Pocket, dancing, singing, dress up, plyign imagintive androle play games, talking with mummy and daddy or others, playing with friends, doing sport.....all manner of things.
I suppose if you have the kind of child who would become fixated on a games console, and do nothing else that play on it, then es - not a good idea and something to avoid. But for the average child - not a problem, although I would wait till school age.