Subnautica is fantastic. A very nice mysterious story and amazing atmosphere. I think you might be able to kill the sea creatures, but I didn't as it is really not the point. If you don't have Thalassophobia yet, you will by the end!
Seconded, Subnautica was an amazing experience. One of my all time favorites, though I'm not sure if it's a good fit to play with your kids (or even with other people in general). The best part of the game is the atmosphere it creates, which means the best way to enjoy it is to really immerse yourself in the experience.
Agreed. And highly recommend playing with music turned off for the most immersive experience IMO. I have some unforgettable moments from that game.
Another vote for subnautica. Best non-violent game that comes to mind first for me.