What do you do with your kids that you never do for yourself?

Almost everything we did came from some idea out of a TV show or movie.
Extensive, whole-room blanket forts - with peep holes at various places - designed so my kids could be the meerkats from the show MeerKat Manor. I spent so much time on them that I'd leave them up for a week or more for increased ROI.

We made movies in a local city-wide contest like 4 years in a row. It all stemmed from us watching Avatar: The Last Airbender movie and them wondering how those special effects work. We made our own cut-in-camera special effects in the backyard that day and proceeded from there.

Last one that comes to mind is fixing a broken MonsterHigh doll knee joint with a finishing nail. Still working 15 years later. I could only last about 10 minutes dressing/redressing/playing-house with those dolls but I probably spent a good 90 minutes perfecting that knee replacement.