I've seen these and they're lovely but I always come back to how long that must take mom or dad to prepare. I know you say it's only about fifteen minutes but I'd probably be at it for a half an hour messing things up. It truly is love in a box.
When I was a kid my mom would sometimes slip notes into my pencil box or notebooks to remind me that she loved me. I kept a lot of them and I'm really glad I did because now that she's passed I can always look at them to remember her. How wonderful to have such a warm tradition to share with your children.