That's what I would do (have done, actually). However, OP and his/her kids probably don't really need the latest Luma features that require B9S, so they could just update...If you have SafeArm9Installer then you probably have A9LH. What happens when you hold Select on boot? Does it tell you what version Luma you have? You will probably want to follow https://3ds.guide/a9lh-to-b9s, but before you update, open the config menu (Select on boot) and make sure boot emuNAND is turned off, and show version string is turned on. Press Start to save and go to System Settings. Make sure the version string starts with "Sys". Then you can update. You will have to set up Gateway again: https://gbatemp.net/threads/tutorial-using-luma3ds-gateway-on-b9s.431691/