You may love planning and organizing but on your big day the last thing you want to do is be running around checking on flower arrangements and putting out fires between squabbling relatives. I've been at weddings with and without a wedding planner and if your budget allows it I highly recommend having a planner on-site. Every wedding has at least one thing go wrong and a planner is able to pounce on it and deal with it without you even knowing about it.
Not only does the planner let you focus completely on your wedding but you have a 3rd party that can enforce any of your rules without you worrying about what Uncle Fred or Cousin Susie might say. You are free relax and enjoy being the centre of attention without giving one thought to the administration of the wedding.
Your wedding day is not the time to be stressed. Having a wedding planner carry that load will make your special day that much more enjoyable.