The book is printed one sided, you don't need to be worry about destroying an illustration on the other side of the page even if your Sharpie or other marker bleeds. Fineliners like Stabilo, Staedtler won't bleed. If you want to be more creative, you can create art journal pages on the other side. 170gsm paper is thick enough to take even some acrylic paints.
I stopped running workshops a few years ago but there are some occasions when I can't say 'no' - this is one of them - I'll have a honour to show how I work at Dizzy Birds Crafts and at the same time celebrate Amanda's birthday!
It will be an amazing day, very creative and relaxing.