Q. Dear Donia,
Thank you, Allison
A. Dear Allison,
I am so sorry to hear about the damage that your mother's notebook has endured. The best thing for you and your children to do is to consult with a conservator to see what can be done. There are a lot of possibilities and a conservator can help you find the right fit for your expectations and budget.
I see from your information that you are in the UK. Like in the US with the American Institute for Conservation's Find a Conservator list, the UK's Institute for Conservation (ICON) also has a conservation register that will help you find an accredited conservator near you.
Good luck with this project. I think it is a great birthday present!