I would tell you which cruise line would be best. As everyone likes different things about cruise ships.
He have done a 23 night transatlantic with Princess cruises with stop over in NY. Other ports being Boston Bar Harbor,Sydney, Quebec City Chartlottetown and Halifax. We really enjoyed this cruise the longest we have done. So are going again this year. No stop over in NY but one in Quebec city overnight.
Next year they are doing a 31 night one which does overnight in NY. If it is something you are interested in.
Hope more people get back to you about other cruise lines so you get more of an idea.
Linda