FB Graph API: Notify friends of current user of activity on my site
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I have a website where users can create events (something like Evite). 
Users log in by authorizing my app on Facebook so I can access all their info and post on their walls.
I have some logic when the user creates an event on my site that allows them to invite people by email and would like to also allow users to invite their Facebook friends (I got to the point where the user sees the list of her FB friends and selects them).

The problem I have right now is that I don't know how to notify the user friends on Facebook. These are the options that I thought of but I don't think any of them will work:

- **Send a private message to each user invited by the current user:** This is just not supported by Facebook (to prevent spammy apps I guess).
- **Show the send dialog (with Fb.ui) prepopulated with the list of users selected by the current user**: Currently the FB API supports only one user name in the prepopulated list.
- **Tag the invited users in the wall post of the activity:** I've tried this without success as they explain it here: http://digitizor.com/2011/01/24/tag-user-facebook-graph/ and http://stackoverflow.com/questions/3099183/tagging-a-user-in-a-wall-post-update-using-facebook-api and I see the documentation but there are no samples and I'm kind of lost.
- **Send a request of my app using FB.ui:** Apparently this is supported only for Canvas apps only and not for websites (https://developers.facebook.com/docs/reference/dialogs/requests/)
- **Send an email to the users' @facebook email address:** There is no way (that I know of) of knowing if a user allows external people to send them email messages to this address, plus the message by default show as plain text and I want an image to be displayed in the message body.

The only feasible option I see right now is using the FB.ui dialog as a second step in the event creation process in my site and having the user manually select her facebook friends in that dialog.

Does anyone have any previous experience with this? Any alternative that I am missing?

Thanks a lot