You may be able to purchase a transfer from Regent when onboard Sheila. You could also contact Revelation tours, their contact is in the guide section, I never remember it right. Its about a half hour drive and Nice is a small airport and easily manageable, I would think if you were off the ship by 9, you shouldn't have a problem.

Last time we were there we had Regent air, and an overnight hotel, so we had Regent transfers from the hotel. Our flight was around 11, so they took us from the hotel at about 830 or so I think.