What are some glute/thigh exercises that won't damage my knees?

Correct technique: Correct technique is the correct way to prevent joint, ligament, and other structure injury. Most exercises, including lifting, is safe provided you use correct technique. Get a coach, start with low weights/high repetitions, and avoid things that cause severe or sharp pain. Lunges, starting without weight, are great for the gluts/thighs. When doing this, keep the front knee behind the toes