Here are a few resources for teaching the sun and moon letters in Arabic:
Brief Shamsiyyah & Qamariyyah lesson – this is an old, quickie lesson, but I thought I would post it because I think it is still useful.
Sun and Moon Letter Online Flashcards, I found these at quizlet (I love quizlet). Do a flashcard drill or play a few simple games to practice
Sun and Moon Sorting Activity - super cute from A Muslim Homeschool
Sun and Moon Letter Poster - very nice visual poster to help distinguish between sun and moon letters from A Muslim Homeschool.