I stayed at the Marco Island Marriott in Nov 98 and was very disappointed. I thought the property was really beginning to show its age. I have stayed at the Hilton also and thought it was a little better, but it is a much smaller resort. As for your teenager, sorry to say I think they will be a little bored. The Marco Island/Naples population has an average age of 70 years old and they roll up the sidewalks at 9 p.m. It will be a very relaxing vacation however.