I'd make a listing for it it on
plugshare.com.
Here's an example of a vacation home listing:
PlugShare - Find Electric Vehicle Charging Locations Near You, but I wouldn't set it to "restricted" like this person did. Restricted locations aren't shown by default, and many users don't even know that there's an option to turn them on. Just make it clear in the description that it's for guests only (as are most hotels and resorts, which are also listed as non-restricted).