Lyn- Yes, I agree, I didn't even think about the 7 day part... to have a chance to see a good variety of ports you need to find a longer cruise. Definitely fly over at least a day or two before the cruise or the jet lag is going to ruin your first couple of days of cruising.
And its the info you provided on the Oceania/Azamara lines that prompted me to suggest finding a TA that can more easily spell out the options available and meet up his preference with a cruise line.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013