I am so sorry that your child has been diagnosed with CML- and at such a young age. Over the years there have been quite a few young people and children who's parents or carers have posted on this forum. As far as I am aware all have done well, either with TKI therapy and/or SCT.
I do hope your child is being treated at a specialist centre that has access to expert CML clinicians. I assume you are in the UK?
There is a facebook group specifically for children with CML- you might find it helpful to speak to other parents who are members on there.
here is the link:
https://www.facebook.com/groups/207664421574/
Meanwhile if you need any support for yourself or advice on available therapies and/or how to deal with side effects etc- please do not hesitate to ask on this forum
Sandy