If students aren’t used to doing good self-evaluations, they’re not any more prepared to do good peer-evaluation. Again, teaching students effective peer evaluation is a crucial part of their learning process. You may choose to have students give each other summative feedback, but in many if not most cases, formative feedback will be the preferred way for them to communicate with each other.
Laura Gibbs uses peer-evaluation extensively in her ungraded courses, and has assembled a useful collection of student-friendly resources on giving as well as receiving feedback.
If you incorporate peer feedback into your course, knowing how to give and receive feedback could possibly be the single most important skill students learn with you. Give it attention, emphasis, and time to develop accordingly.