Mine went out last week and ours is on the 10th. I think next week is good. It gives people a chance to get it on their calendars before anything else . I think at least 4 weeks is a good lead time.
I think you should send them out as soon as possible, that is thanksgiving weekend and people may already have plans or be starting to make plans, they should have a heads up.
Mine went out a month early. But that's only because I got them a lot earlier than I thought I would. I planned 3 weeks prior. But that's cause it's around thanksgiving and people have plans I wanted them to have plenty of notice.
Re: how soon?