Here are a few suggestions. First, I would suggest soy nuts. They are available here salted or in a bbq flavor. My kids like them and they are loaded with protein. Also cottage cheese is a good source of protein. You can add soy protein supplement to almost anything: pudding, fruit, oatmeal, applesauce. I use the vanilla soy protein powder. Tempeh seems to be more popular with my kids than tofu. I use it is spaghetti and stirfry. Tufu can be used in pudding, dips, and other snack type creations as long as it is kind of disguised. My eldest daughter is getting into all kinds of Asian mythology and history at the moment so tufu and tempeh are at least in her realm of interest. Good luck.