I would urge you to reconsider not going on a day when SeaWorld is offering their Christmas Celebration events. I, too, have no love of winter (living in Canada, we get WAY more than our share of cold and snow) but the SeaWorld holiday events are OUTSTANDING. It's also included with your regular park admission, so truly....you have nothing to lose and everything to gain by going. Oh Wondrous Night is simply spectacular: if you saw nothing else at SeaWorld this December, THIS would be my foremost "do NOT miss".
The only "don't bother" item, in my opinion, are the swan boats. They cost extra and they are frustrating to navigate.
For animal feedings, we found the shark feeding to be "meh". The sting rays and the sea lions are super fun to feed, so budget for a tray of food or two.
If you want to get up close with a dolphin but don't want to break the bank, sign up for the dolphin encounter. Its a steal at $15 a person and the photographers get AWESOME pictures (which are an extra cost, no obligation to purchase though).
Coaster lovers should not miss Manta, Mako and Kraken. Journey to Atlantis is another favourite of my thrill-enthusiast husband.
Don't pass by the Aquariums at Manta and Journey to Atlantis. They are fantastic and worth a few minute of your day.
All of the shows are awesome. Blue Horizons is a family favourite in particular. Clyde & Seamore, Pets Ahoy and One Ocean are also fabulously done.