We did a private excursion, dropping us at the airport Hilton. No, its not crazy to do a Princess tour, but I think, as you can customize a private tour, the better option would be a private tour. That will help you perhaps see something you haven't seen before. Rome in Limo is wonderful for this.
Now taking a tour that drops you back at Civi, and THEN a taxi to the airport, does sound a little crazy to me.