I have the slice of life mod and was also was invited to Sylvan Glade. And I have a husband and wife (husband is a vampire and the wife is pregnant). It was a ghost inviting them (though the invitation was worded differently from yours). The husband was invited, but I had the wife go, too. Now they are all just standing there chatting and intermittently vomiting (the ghost keeps vomiting too). I just had them stay, because I was hoping there was some sort of propose to meeting this ghost in this location...less than two hours left in the event, so I guess we'll see if anything happens!