fazy,
I would suggest you start with equations. I do 9 equations a day, but split them in the sessions. That is the only way my daughter keeps her attention. I also would suggest that you keep teaching you son the rest of the numbers up to 100. Have you read Doman's both "How to teach you baby math" or have you read some of the posts here about teaching math?
Hope this helps!
Let us know if you have any more questions.