The most common symptom of fifth disease is a bright red raised rash that appears first on the face, and then (a day later) on the arms, legs and trunk of the body. Children may have mild flu-like or cold-like symptoms before the rash surfaces, such as a low fever, sore throat and headache.
At your wedding you can play any kind of music you want to. Get a dj or band who plays a wide variety of music and decide what moods you'd like to set for different times during the wedding & reception. There are traditional songs played at a lot of weddings but do what makes the two of you happy.
If your wedding is an evening wedding, guests should know this, since it's a typical rule of etiquette. You can write on the invitation, Black tie invited so that your guests know that it's a formal wedding. Based on your description of what you want them to wear, this is considered formal wear.