It's a good idea for Dojos to use tried-and-tested pre-written learning resources; they save you having to plan the specifics of projects that your Ninjas may want to do. This makes life easier for the Dojo team and reduces the amount of work mentors need to do!
Another great benefit of these resources is that each Ninja can have their own copy, either printed out or on the screen in front of them, allowing them to move through the material at their own pace. Mentors are available to support Ninjas who have issues, but they don’t need to actively walk them through each step.
You can either choose a specific project for all your Ninjas to work on at the same time, which is a good approach for new Dojos, or have Ninjas work with mentors to choose projects that meet their particular needs and learning goals.
You can find a collection of educational resources for a variety of programming languages and hardware projects on the Raspberry Pi projects site, including materials from the CoderDojo Foundation team and the broader Raspberry Pi Foundation team.