Dining reservations open at 7am, Fantasmic tickets at 8am, unless its changed recently. The direct line to the event tickets(Fantasmic) is (714) 781-4400. Start calling 5-10 minutes early and just continue until you get through. The email above can be used for general requests, but you will need to call with your credit card number, so for Fantasmic tickets I would call (714) 300-7526 Option # 2 if you want them to make the reservations for you. I don't think they "guarantee" anything, but obviously they have the inside track on gtting the tickets. I've never heard of vacation planning not getting tickets when requested. You must be a guest of a Disney resort to use this service.
Yes, today they would be booking Fantasmic for Dec 12. If in doubt call today and ask what day you need to call for tickets.