If you're really that concerned about someone finding your IP:
1) As Lunorian said, what is your site? What kind of admins do you not trust that you still give admin/mod priveliges? And what do you think these people are going to do if they do know your IP address? Which they realistically do at this point if you've already made them admins/mods and your IP wasn't hidden in the ACP that they could presumably also access.
2) Get a VPN. Regardless of if you can manage to disable logging in MyBB, your PHP installation will probably log user data and your hosting provider will also probably log usage data, all of which may or may not include IP addresses of users. A VPN ensures your real IP isn't visible to any site you connect to, only the IP of the VPN server you're connected to.