Did your child ever tell you that "everyone" bosses him (or her) around? Why not show your love by letting them be in charge for the day? You can give them a "menu" of choices, from a picnic in the park (if weather allows) or a day at the movies or a romp in the ball pits at Chuck E. Cheese's.
If you're hoping to broaden their horizons, their "menu" of choices might include local museums, botanical gardens, nature preserves, aquariums, amusement parks, airfields and walking tours. Just keep in mind that area attractions could be crowded on Valentine's Day.
Alternatively, if you want to spend some time getting cultured at home, rent a movie about a faraway place that they'd like to visit or an historical movie about how we landed on the moon.