In that case I would change the "ages served" on my State website, local daycare page, and any advertisement sites I subscribed to (care.com, sittercity, etc.).
Then I'd send home a letter stating that as of September 1st, 2018 I would no longer provide care for children under ___ age in order to focus on ____.
I added some tags for a niche but I don't think you can see them unless you are a member.