Can I turn off my Guest account and still use Find My Mac? I understand that turning on Find My Mac also turns on a "Guest" account (in "login only" mode). For a variety of reasons, I would prefer not to have an enabled Guest account at all. 

Does Find My Mac still function with the Guest account turned off? Is its functionality limited in some way by the absence of the Guest account. Or will the Guest account be re-enabled by Find My Mac when I reboot?
Yes, it will still function without the guest account.  However, in order for Find my Mac to locate your Mac, the Mac needs to be connected to the internet.  If your account is secure and your Mac is stolen, presumably the thief would not know your password, and so wouldn't be able to login and join a WiFi network.

Leaving guest access enabled allows them to login without a password, in the hopes that they then join a WiFi network and your Mac is located (and immediately locked/wiped/etc).