The Fantasmic package is really nice because it guarantees you a seat for the first show which is usually busier than the later show. Last year we went on January 4 to the second show and there was plenty of good seating left. If you are good with the second show, you probably don't need the package but if you want the first show, you should really get it for peace of mind that your seat is reserved. Fantasmic is a great show!
You didn't say whether you had kids or not but either way, the Brown Derby is one of my top 3 favorites on property for the awesome cobb salad and filet with mashed potatoes. It is 2 credits but worth it I think. I went there as a kid and enjoyed it then too.