Wow - your DS must love math! The lunch box is a great idea if I can ever get discipline enough to do something like that consistently. Good luck to your DS next week.
He does love math. He goes to school early 2 or 3 times a week to work on problem solving test like mentioned above. He cannot participate in math counts competition since he is in 5th grade but hangs out with the other kids who do.
The National Math Counts Champion in 2012 went to his school.
We did a competition in spring and fall of this year and he loves it.
I just have to keep an eye out for signs of burn out. Nothing so far.