So why didn't they just use Mad Hatter?

Thoughout ror and ww, Mad Hatter was never mentioned as if he didn't exist. Considering the plot, using Mad Hatter himself as Red's tutor in ror and the villain in ww, is no big deal.

Why should they have made his son and grandson?

Also, Mad Hatter saw his son sent to the Isle of the Lost. It would be interesting to see that in the plot though