Didn't have a pre cruise package. Stayed at the Banks Mansion Hotel. It's right in the middle of everything, close to Rembrandt square. Walked everywhere, Anne Frank house + other museums. Great restaurants also close by. I drove my rent car into town to drop off wife & bags at hotel. DO NOT do this. Driving in old town Amsterdam is crazy. Just drop car at airport and take a cab.
Tour of Marksburg Castle was well done but be warned the walking is over very rough rocks and up some steep hills. If not in decent shape think about doing something else. The castle was in good condition and I especially enjoyed their display of soldiers armor through the ages. They have a small cafe and gift shop at the end of the tour if you need a snack or WC.
After Koblenz they take you to Rudesheim for a walking tour of the little town. I could have skipped this as there is nothing really to see other than some shops in a nice pedestrian only area. As we were bused in there was no choice but to walk around for an hour+. This is the day we had to change ships so we were stuck but I'm thinking on a normal trip you could just stay aboard.