Adjusting Minecraft for ‘appropriate’ play: reply to a parent.
Using spawn eggs in creative, and hitting each other (which does cause damage) in survival, should not be allowed. Minecraft is SUCH an open-ended game that certain aspects of it need to be filtered in order to facilitate the right kind of environment and behaviours that are socially acceptable in all facets of online and in-game play. We don’t let our children hit each other in real life, and we shouldn’t let them hit (and kill) each other in a game. (That is also, partially, why this game is rated 10+). Kids also get very easily distracted, so there are other things that need to be adjusted within a world and the game itself to help them focus on the task at hand, be it building something epic together, or surviving a night alone.
Private and public Minecraft servers use plugins to adjust Vanilla settings and add on to the game. We use a host of plugins, some of them custom built for learning within our worlds. There are other things, too, that you will have to adjust manually, but this takes some experience and knowledge of the game. I also suggest that you have a parent attend at all times while they play, and play with them in the game, if you can. That would be the best way to learn!
Stopping fire from spreading, keeping inventory on so that when you die you don’t lose all of your items, and preventing mob-griefing are a few of the important things to adjust (called gamerules).
MinecraftEDU (which is a mod) can do this for you, too, but there is a learning curve to it.
It will be important to learn as much as you can. Watch videos, and if there is something that happens that instinctively you realize as a parent is NOT appropriate, then tell them to stop (for instance, trolling each other by breaking blocks underneath someone who is ‘afk’ and them pouring lava on them to kill them).