Think your wife is RIGHT,,for first cruise
I think 3 wks TOO LONG. You might not like it (hard to believe,but true).Some get sea sick,for instance.
Maybe the Med.would be a good option,since not far to go and wonderful area.
Think of it as your FIRST cruise,then can change what you liked or didnt like.Perhaps ship too big, cabin too small, itinerary not right,etc.
We started on the larger RCL ships,but found we preferred smaller(700 or less passengers ,such as more luxury lines like Regent,etc)and limit our cruise to 2wks MAX>we like to have a day in ea.port before and after.That way you don t have to rush off ship to make air arrangements.Seems everyone want s to be FIRST ONE OFF AND ON ship.
Let us know what you decide.Lots to consider,I know.