Just finished cruise 16 and 17 with Carnival. Miracle is a great ship. She has a lot of charm! We are in our 50s (me) 60s (hubby) and have never found Carnival to be overly party party ships. If you hang out at bars, you will find drinkers. We drink but not much and have never found a place for quiet, or comedy, or movies, or sports or a party late at night up on the Lido. We actually run so much during the day that we go to bed fairly early at times and have no trouble sleeping.
I think you will have a great time ! Enjoy your cruise !