(hold it and hold on are both fine and you can also use watch your step)
This is regular drill I have with my children every day:
Me: "Come on kids, up the stairs, it's shower time now. Be careful, hold on tight and watch your step. Please put your clothes in the wash basket too, not on the floor."
Kids: Awwww. But I'm not tired. I don't want to go to bed. I'm hungry............ (and many other complaints and excuses to try and not go to bed which never work :D)