Hi Kate,
My husband and I really enjoy a night out of adult dining while at Walt Disney World. You have eaten at some great restaurants, and based on those, I can make some recommendations that I think you'll enjoy. All of these are slightly more upscale table service restaurants. I can tell that you are open to dining at the resorts, which opens up a whole world of possibilities!
Since you mentioned Coral Reef, I suggest Flying Fish Cafe in Disney's BoardWalk Area. This is a seafood-focused restaurant. Much of the food is cooked over a wood fire and is delicious. Knowing that you enjoyed Boma tells me that you are adventurous eaters - so head across the hall to Jiko, also located in Disney's Animal Kingdom Lodge. Jiko offers African, Indian, and Mediterranean cuisine, and features the largest South African wine list outside of South Africa.
California Grill is a lovely restaurant with great food. Why not head downstairs at Disney's Grand Floridian Resort and Spa to Citricos? Citricos offers Southern European fare with a lovely ambiance and great food. Since you mentioned Captain's Grille, I again suggest staying in that resort area and heading to Yachtsman Steakhouse at the Disney's Yacht Club Resort. This is a steakhouse with delicious food.
One final thought for you - you will be visiting during the
Epcot International Food and Wine Festival. Considering that you are traveling with a party of people who enjoy good food, definitely check it out. You can sample tapas-sized portions of international fare from kiosks as you walk around Epcot's World Showcase. There are also typically special offerings such as special dinners and presentations during this time. Monitor the website for details!
Have a great trip, Kate, and happy eating!