I do this each year in my own classroom by giving each student 10 or 12 random hearts (they can swap if they want) and let students write their own Valentine letter based on their heart candies. Kids have loved it for 15 years.
Sweet "Love Bird" Valentine's Day Brunch // Hostess with the Mostess®
One of my student's mom made those puff balls for my class and they look so beautiful and festive hanging from the ceiling. She says they are easy to make too.
Easy DIY I heart you marshmallows. Give as Valentine's Day treats or stick a bunch of them in a small tin bucket filled with red hots or message hearts or red, white and pink M and Ms for a Valentine's Day table centerpiece or gift.