If you're going to do an ad-hoc profile (which isn't cheating by the way), then you need to add all their devices to your account as test devices. The ad-hoc profile must then contain all their device IDs and then you would have to destribute it to them.
Easist distribution method I know of is TestFlight. There are ways to post it to a download link and upload a manifest file so all they have to do is click a link, but TestFlight is far easier in my opinion. TestFlight will also send notifications when you upload a new version to the user, so all they have to do is click a link in an email to go download the new version.
Doing ad-hoc also means the profile will expire (as will the app), and if a user gets a new device, it will have to be added to the profile and redistributed again.
Personally, I think it's easier to get it onto the app store so any number of users can download it at any time.