We told our parents and my sister right away.
I told my boss right after my first doctors appointment.
We wanted to wait until after the first trimester to tell our friends, but I was coaching cheerleading with 2 of them and knew I had to tell them because I could no longer demo stunts/tumbling. Since we had to tell them and we knew news would spread anyway, we just told our whole "group" of friends. That was at around 8-9 weeks.
As far as your wedding, I would just tell the people you're concerned about that the wedding will not be in September, but you're not sure when yet. They may be a little confused at first, but in a couple of months when they find out about your pregnancy they will understand.
As far as your job, I would realistically think to yourself if your boss will have some sort of alternate assignment for you. If not, I would start looking for other work - or try to see if you can swing it financially to take the summer off. Then I would wait until a little later in your pregnancy to discuss with your employer.
It's nice to be important, but it's more important to be nice.