There are quite a lot of kids games for the ps3, Amazons top picks are:
http://www.amazon.co.uk/PS3-games-for-children/lm/R34HFUHB9QHPNZ
The new Xbox One has just been released, so has a very high price tag of around £430
http://www.amazon.co.uk/Microsoft-7UV-00080-Xbox-One-Console/dp/B00BE4OUBG
The games for the Xbox One will also be more expensive and there won't be as many to choose from as compared to ps3 at the moment.
The previous version was the Xbox 36whaling is cheaper and has lots of cheaper games to however these days a lot of game developers make versions for Xbox and ps3 so if you are thinking of switching console for just different game choice you would be disappointed. In my opinion there is no point switch between the old ps3 and old Xbox