Hi Alexia,
I just read your brief and it sounds like your project is perfect for me. I'm a traditionally trained artist and I've been working as an old-school illustrator for many years. With children's books illustrations I mostly work in mixed medium of pen and ink and rich water colours, exactly the medium you mention as preferable in your brief. Some of the samples are available in the portfolio section at https://www.freelancer.com/u/ddimitrovska.
As for the process of work, I normally first deliver pencil sketches and proceed with inking and colouring after they are approved by the client, meaning that they can be revised as many times as necessary while in pencil. Once inked or coloured though, illustration can only go through minor changes, if at all. I deliver high resolution scans. Upon full payment, you'd own full copyrights to the illustrations for any future use. Acknowledgement of authorship would be nice, but not necessary.
If you are interested, please contact me to discuss further details over chat. I'd be very happy to hear from you,
Kind regards,
Dusica