Multiple domains on one hosting account

I have a client who wants to host multiple sites on the one hosting account. I don’t have a problem with that and have a suitable hosting service that will allow up to 10 sub domains and 10 addon domains on the account. That also means a total of 10 databases which I believe equates to 10 separate WordPress installations.

But there’s something additional she wants to do on her main website. She wants to be able to do a page that is dedicated to each of her clients. She works for a charity and her clients are babies that die of a particular condition. So I’m trying to work out what’s best for her so we don’t have multiple WordPress installations. Would be best to do folders that work like this: https://www.herdomain.com/babya https://www.herdomain.com/babyb or would there be a better way of doing this do you think?