I have developped educational software on my web site . Among them Mathrace, a 3D arithmetic race to learn times tables.
All along the race the pilot faces different kinds of arithmetic problems under the form of panels. Without stopping his progression he has to determine the correct answer and to drive towards it.
For even more fun, a double players mode allows to compete simultaneously against another pilot. The level of difficulty can be tuned independently for each player so it is possible to get fair races with players having different arithmetic skills.
This could be a good product for kids; however, Central Ohio school systems told kids not to learn multiplication tables ten years ago - so market it to parents opr clubs, possibly tutors. And other school systems that haven't banned learning times tables.