At the time, we had a bed with a frame that worked perfectly:
Talia was little when I did this, so her main role was to pass me pieces of string (and she was quite happy with the task). Now, we could make this Valentine surprise from her, for Daddy, and she could be part of coming up with the reasons, cutting out the hearts, maybe decorating them, or drawing pictures of things she loves.
Have fun with this one- if anyone does it, let me know & I'd love to see pictures! :)
Edited to add a similar idea that I love- having an"appreciation day" for someone you love, and using balloons with notes around the house.