Your boss would never send you to these ports on business
Both my DH and I traveled on business quite a bit, visited all major capitals in the world and many business centers but never went on a cruise. I also was worries about getting sea sick, as I get motion sickness easily. We committed to doing this Western Mediterranean cruise to visit places in Spain, Italy and France. Overall this was very positive experience, I encourage anyone to do this.
One observation: get some cash in EU before you get on the ship. You'd have to pay all train tickets in cash and it's precious time in the morning to get to a a train/boat/bus instead of looking for an ATM machine. ATM on the ship is in USD. Daily Compass paper give you small maps and highlight for places to visit - be sure to read and take it with you. It also has phone number for the ship in case of emergency. As a cruise prep I recommend to get one of tour books - we have Rick Steves guide to Europe. Remember, prices outlined in all books go up each year. I was preparing to details - where to get tickets, which train to take, which street to go. Don't worry that much. You get some information from the ship and people speak English in all these touristy places.
Hint. Just few days before leaving DH called Expedia and got ~250 USD in on-board credit because RCI was running a sale.
Voyager is a great ship, it's big and very stable. On a day one at sea we have two meter swells - it was just a bit of shaking, like going in a train. We did all excursions on our own and it was easy to prepare and easy to do.