I'm not Sue but I can answer your questions. The Happy Haunts tour I believe is for the Halloween season. If you are going in December, you will be in the Christmas season. There is a tour for that season, it's the Holiday Tour. We have done this and it's great, we will do it again if we go back this year as it was a fun/interesting tour. It is a DL park and a guide takes you around the park showing you many of the holiday traditions and you have a ride on the Haunted Mansion, then you go to Toon Town and you get a really cute mug with hot chocolate and a gingerbread man, you then head over to some private reserved seating for the parade.
The Fantasmic dinner package is at WDW. At DL they have the Fantasmic Dessert Package. You prepurchase tickets to the event, then earlier in the day/afternoon, you have to go and line up (get there early) and register and choose your seats (the reason to get there early). Then you return at before Fantasmic starts to your assigned seats and you are given hot chocolate and a dessert container. It's good to stick around after to watch the fireworks as it's great viewing from there too. They also have a similar package available for World of Colour at DCA park
The packages are well worth it
If you have any allergies, you just tell them and I was really lucky, I got the platter below and another whole platter with fruit in it. It was so much food I ended up sharing my fruit platter with the whole little seating area we were in.