Trouble with Endings!

I'm in the process of finishing a book, the third one in the Hazlett Series -- Cleome's Garden. The problem is that I am trying to wrap up the whole series by the time I type THE END on this one.
I'm having trouble visualizing the ending. My characters keep moving around, saying things I don't want them to say. They aren't helping me!

It might be that I have just too many people involved, but the heroine and hero of the first book are getting married, so everyone -- or just about everyone -- has to be there. And then I have to say good-bye to all of them.

Maybe saying good-bye is what I'm having trouble with. I've created a town and a group of people who are very special, who in their own way are doing the best they can to make the world better -- or at least their own little corner of it.

Why would I want to say good-bye?