How should I tell this mom that I'm taking 1 more child into my care?

When I advertised I told parents that I will be taking only 3 kids and I charge them slightly more then any other day homes. Now, I've replaced 2 of my old families and my new families would care less. I will inform them about the changes.

From October I'lI have 1, 15 months old, 2,12months old and one 22 month old. If I take the new client. Here is why i feel a little nervous. One of my part time clients asked me if i could have her child 1more day for temp? This means i will have 4kids in one day. I asked one of my clients if she would be ok with this and she said she does trust my ability to look after all 4 of them but what happens if there is an emergency(this was the reason for my "emergency"post) as I live in an apartment? I understand her concern and would think the same if I have a child in care and im doing my best to find a solution in case of an emergency.

In October I will have 2, 12 month and 1, 15 and 1, 22 month. Do you think I'm crazy to take on 3small kids? I will hire a part time help but that would be only part time and there will be 4kids only for 3 days.

Now the question is, how to break the news? Our 6 month contract is already ended and I need to write a new contract. I love this family and their kid but at the end I will do whatever best for me and for my business.

I've told her that I will email her the new contract. Shall I mention it on the email or call her my home? I was thinking of calling them here over the weekend to talk about it.

What do you all think?

Thanks ladies.