While the Holland-America Line is the official Maggie's Farm line, we'll go out on a limb to recommend Seabourn - "the best small-ship cruise line." They are, with no more than 200 suites/ship. They have some special deals right now.
Seabourn is more for grown-ups, while Holland-America can accommodate well-behaved kids who do not mind dressing for dinner.
Every couple of years, we'll do a Med cruise or a Euroland river cruise for a change of pace instead of grabbing a rental car and driving all over. Good fun, never have to move your stuff, 24 hr/day service, and enjoy being at sea between cool destinations. I love being at sea.