It's awesome you were able to get your kids involved with this!
I think it's a decent start to a platformer. I agree the enemy hitboxes could be tweaked. Good practice is to make enemy hit boxes slightly smaller than you think they should be because it feels more fair to the player.
I would've liked a quick reload option. Like just hitting R to reload the level since it's possible to get stuck and be unable to jump back up. And if you develop this more I think it's worth tweaking jump speed and gravity to get it feeling just right.
Great work! This is my first Trijam as well and 3 hours goes by so, so fast.