You due end of February?

I not think unreasonable to wait until mid-September. It only three more week. Some might be wondering if they have noticed but if they not asking, it up to you when to announce.

What you write when you do announce will depend on what you planning to do.

Are you going to close?
Are you going to stay open?
Are you reduce numbers?
Are you closing short term - how long?

Unless you know these things, little point in announcing. If you just announce pregnancy and no information about effect on business, parent be asking all these things. If you not have answers yet, then all will happen is concern and fretting from client who might start look elsewhere.

I just believe if making announcement, need to have idea of effects and be able answer their questions. Otherwise, it cause concern.