We have been going to WDW over Thanksgiving week for a number of years. 8 people on Wednesday is going to be tough. But, as everyone says things come up all the time so don't give up and definitely sign up for TP reservation finder. It is going to be very busy so make sure you get all your FP at 60 days 7am.
There are tables for 8 available for lunch on Wednesday where you can take a mid day break and grab a quick bite for dinner at HS before Fantasmic. Within walking or boat ride - Captain's Grill, Biergarten at EPCOT (if you have hoppers - fun for a big group), ESPN. With lunch, if you do have to leave you won't be rushed to get back to HS.
If you are set on dinner, have a late QS lunch, you can go to the 1st Fantasmic (there will most likely be 2 that week) and have dinner when you leave the park. Flying Fish is available and is nice to stroll along the BW. Shula's (no
DDP accepted) is also available over at the Dolphin. If you want a late dinner Yachtsman has late availability.
You are doing a lot of traveling on Thanksgiving. Traveling from AK over to the BW for Flying Fish and then back to MK is a lot unless you have a car. Buses will be very crowded and will take a lot of time. I would keep trying for a lunch at AKL (Sanaa is available - so is Rainforest at AK but not sure if that is your cup of tea) or something on the monorail before you head to MK. I see 2 reservations now for 4 each at GF Cafe; one at 6:50 and one at 7:05pm, same with The Wave 6:50 and 7:15.
Friday will be the 1st night of the Candlelight Processional so Illuminations will be at 9:30pm. Holidays Around the World will also start that night. I would try for dinner at EPCOT. If you do Captain's Grill on Wed, Biergarten is available Friday, and so are the places in Mexico, late lunch at Coral Reef, and a few others.
As others (and you

)have said, if you have your heart set on the reservations you have, keep them and try for a party of 4 around the same time.
Good Luck!