Im my own lesser known frontend, MultiFE (yes I known), you can passcode protect any library (which I call in MultiFE, due it also for albums. singles, pc games too) with the main password (set in config), and each library can been shown (but protected) or been hided. I think you could in MultiFe just create 2 M.A.M.E libraries, one "cripplede" with some genres without password and one with the main password with all games. The passcode also used for admin/quit features as well.
No keyboard for password required.
For other frontends, I think the headkaze login can do the job. I do have not tested it.