Yes, the message to buyer is very important because, frankly, almost none of our customers read our shop announcements. Usually they find an item they like and never even end up on our shop pages.
But be warned that not all customers will be amused to hear of the delay in shipping AFTER they made their purchase.
Even if you stated it in all the obvious places (most customers don't read, not even that message to buyer).
I used to ship within 1 business day. So my customers would not be happy if I suddenly informed them it would take 2 weeks to ship their order.