I teach 4-80 year olds on a regular basis. I agree 30 min -45 at most is best for 4 -5year olds. Most Children love Waltz and I highly recommend you start with this dance. If you teach Swing for "fun" right away (without many years of teaching experience)it can lead to very poor habits for a very long time.Box,Progressive and Bow will make a good class session.