If you watch TV on other Sundays, that is an indicator that you don't believe it is spiritually harmful. Arbitrarily creating a rule/tradition about one Sunday in the name of keeping the sabbath is extremely inconsistent.

The only lessons I can think of that teaching are wrong. It's only important to follow the sabbath if others are watching? Commandments are only important when they are least inconvenient?

I really am curious. I worry that approach is more likely to engender feelings of resentment in your kids, because it is a rule that doesn't make sense.