I highly recommend the following Sudoku site for kids:
http://www.sonokids.com/sudoku/ It uses symbols, so no one can complain that they're "not good with numbers" (you know who you are).
It also uses sounds - it's actually for blind kids, but I was hoping my nearly-blind father could use it - but I do
not recommend playing the game while Eric is within earshot. Every time I click on the cow, Eric runs to the door and barks till the cows come home. He's ok with "Hello" and the flower, but he also barks at the milk, I suppose because it's cow-related.
Play the game and you'll see what I mean, except that when the cow moos in the UK, Eric probably won't bark in the US.
P.S. the game is a 4x4 Sudoku puzzle. It uses a 4x4 set of keys on the keyboard to correspond to the 4x4 cells:
1234
qwer
asdf
zxcv
When you hit a key, it makes the sound, if any, of the symbol in the corresponding cell. To enter a symbol, hit the spacebar, then the key.