Unless they specifically want a puppy from you, most will have found one by then so to have them come over now you will just be wasting your time, as most likely they will not wait that long for your litter. I tell people when I anticipate my bitch being bred and tell them to keep in touch via email and when it gets closer we can meet. It is a good way to weed out who is serious, some will keep in touch and some will not. Then when it is within a month of when the bitch should be coming in, at that point is when I will start meeting with people.