I just received the book this week and made the Noah Ark with the help of my three years old daughter. She did roll balls of marzipan to make the animals' head. I had never worked with rolled fondant before, but found it quite easy... though I must admit I did work a lot with polymer clay in the past.
The pictures and instructions are really clear and helpful. I especially like the chart at the beginning with the exact measurements of ingredients needed for each cake, so you don't end up baking too much or too little dough. The designs are adorable and suitable from baby shower to young teenagers' birthday. Very little sculpting skills are needed to model these cute caracthers. I really think a child 8 y.o. and older could create them successfully. If you can play with playdough you can make those cake. Of course, it does take longer than making a cake out of a mix box, but it really worth the effort. If you don't care much for rolled fondant, you can always cover you cake with marzipan... my kids like marzipan a lot more than buttercream icing!
This book is a good introduction on sculpted cakes that makes me want to explore this art further. Now I need more books from Debbie Brown!