Clearly they don’t understand how serious and important being a member of a lifeboat crew is. Your obviously more mature than they are (if they’re not on the boat themselves)
Being on a crew is a job for a responsible individual. Sounds like your better off without them, you can get your own kids your don’t need friends acting like them too.
Your marking a line in the sand to them that they’re actions could, as you say, have costs lives and they clearly do not understand that.
Stick with what got you the job on the crew, maturity – Sod the kids till they grow up.