Congrats on your new safe. The recommendation that I have always heard is Ammo and powder should not go in a metal container. I have always heard keep it in some sort of wood container, so if there is a fire, the pressure is released easier. I think you are right one with the child safety thing. Just keep it locked. My cat likes to get in my safe and squeeze into the back. That is a little bit of a pain, but children are a little easier to stop from doing that. I have my combo stored with family elsewhere in a bunch of files in case someone needs it some day. As far as family safety goes, the best thing is to not let everyone know what you have. If you can, put your safe in an area out of view. If you have someone come over that needs to be in the same area as it, I have always just thrown a sheet or something over it. I'm sure they assume its just an antique cabinet we don't use or something like that. Make sure you bolt your safe down also. If you have the resources and it works with your house, you could always a little locking closet type thing for the same to be in.
Enjoy your new safe!