Just use a composition book and use white acrylic paint for primer. Then paint it how you want and you can use the stickers for scrapebooking for the decorations.
This was my son's nature journal. (10 yr old)
This was my oldest one's journal and she was proud with how it came out. (12 yr old)
This is my youngest's journal and she said she worked hard on it. (7yr old)
This is the one I created. Everyone who knows me, knows I have to try it too. I was excited when we did this and I enjoyed every minute of it.