If your children are attracted to your guitar and risk making it a wreck, but even if they are only attracted to musical instruments for them and want to create a themed game, here is the tutorial Make it Love it that teaches how to build a multilayer cardboard guitar with very few materials and little work. You do not need great skills, just a little ‘time to create.
You will need to cut out of the box following the pattern and then provided free of colored strings or rubber bands, a pencil and cut into sticks of hot glue. Following the tutorial full of photographs documenting the entire procedure step by step: Cut the shapes, paste them one on top and add the pencils to create the bridges that hold the strings.