DEAR HARRIETTE: I have a question about bedtimes. My kids have always had a bedtime that is relatively early because I want to make sure that they get enough rest and are sharp the next day. Now that they are a little older — eighth grade twins — they are fighting me about staying up late. They want to go from a 9:30 p.m. bedtime to no curfew, especially on weekends. I am willing to budge a bit, b…