Are they being loud because they are bored? Watching tv for the whole nap time can be boring for some kids as some kids don't watch a lot of tv at home. I have a 4 year old girl who doesn't nap most days but she lays down for 30 mins and then I allow her to get up and she comes upstairs with me. I put the cartoons on but she is allowed to read, do puzzles or play with the few toys I keep in my living room. Sometimes I bring out workbooks or colouring books for her to do as well.