My wife and I have been to Curacao three times in the last six years and can tell you that it is one of our favorite ports! We have found the local people to be very friendly and the shopping there is surprisingly good. There is a shopping area very close to where the Adventure docks, but if you can handle walking about a mile, you can take the pedestrian (flotation) bridge across to the main part of town where most of the markets are. So unless you want to see the rest of the Island, I don't know that a tour is necessary.
Good luck and have a great time!