I am trying to make a service that allows users to share party invitations via the Facebook UI/API. What I want to do is send a custom link to each recipient the user designates so that the invitation can be customized and the RSVP form prefilled. I've looked in to the Messenger send method, but that looks like it only works with users that have already interacted with the app. What I'm looking at now is the send dialog, which does more or less what I'm looking for, but it only allows for prefilling one recipient user, and even if multiple users are selected I can't customize the link that each one gets.
The best solution I can come up with is to list the user's friends, and have a send button next to each one that sends my customized URL using the send dialog. This would mean the user interacting with the dialog repeatedly, which is obviously less than ideal. And there is also the downside that the user might add in other friends' names to the dialog, making them get an RSVP URL customized for another user.
Is there any good way to do this? Solutions in JavaScript or PHP are preferred, but I'm willing to try other languages if it would help.