Nuts, including peanuts, cashews, almonds and walnuts all contain protein, as do seeds such as sesame seeds and sunflower seeds. Because most nuts and seeds are high in fat, you don't want to make them your primary source of protein. But they're great as a post-workout or occasional snack. Nut butter is delicious as well, and most kids, of course, love peanut butter. Try soy nut butter or cashew nut butter for a little variety if you're bored of peanut butter.