I am a single parent, so every Valentine's Day, I cook shrimp fettuccine for my two daughters, and I buy chocolate-covered strawberries for each of my girls. I spend the evening with them and explain the meaning of love, friendship and having/being a family.
Even the busiest parents can get involved in the classroom without spending time they don't have or stretching themselves too thin. The secret is knowing which small-scale ideas have a big impact.