Grand one yacht with dinner (catering from Grand Floridian, I got prices and they aren't too bad for the catering) with wishes viewing.
Or the pontoon wishes viewing. I had my cake on there and it was great, it comes with drinks and snacks too. But may be squishy for that many people.
For my 40th. We had dinner at 1900 Park Fare, then went down to the marina did the Wishes cruise and had the cake there. It was decorated with balloons and banners that the kids all kept after. The cake was spectacular, the driver was AWESOME. It was a fantastic night, wonderful way to view the fireworks.
Look at Lurky Loo's posts (think that's her name), she has a website too with all the details, I'll try and find it and maybe do a private dessert party. I think you can have them at EPCOT for illuminations, with your own private viewing area. I think there are other options too for a private dessert party. It doesn't seem too expensive either.
I'll look for the info.