First of all, congratulations on making the appointment. It's a big decision and a big step.
My first days after extractions were very similar to Scaredstiff's and that seems to be "average" In all fairness to you I have to say that what you experience might be different. How it all goes depends on you (peoples systems react differently to pain and trauma) and your dentist (no two dentists practice the same treatment the same way). If your procedure goes more or less normally, you should be able to attend the wedding and have some fun. However, I wouldn't set your expectations for singing and dining too high
Having said that, if your extractions go normally your face sholdn't be swollen or black 'n blue. Any swelling should be restricted to your gums and the immediate denture should help with that as well. Hopefully, after 8 days, any swelling of your gums will be gone, they will have started to shrink and the dentures will be starting to get loose. If you need to use glue do your best to keep the glue out of the extraction sites. Fortunately, the glue can be put on the palatte of an upper denture. You may experience pain from the extractions for a few days but after a week it should be gone unless there was some kind of complication.
When it comes to speaking with dentures, different people have different problems with different letters. "S" is the most common letter to have problems with but other letters that rely on the tongue interacting with the roof of the mouth or teeth could be a problem too. Just for fun, recite the alphabet and pay attention to how you form the letters. The easiest way to overcome pronunciation problems is to practice by reading aloud. After almost 6 months I still can't quite get the hang of S's. Fortunately, everybody thinks the way I say them now is the normal way for me to say it. Time works wonders
I hope this helps to ease some of your concerns. Oh ya, one last thing. If you can't eat or speak well at the wedding at least you'll be able to flash a big beautiful smile!!