Hi Florance, we did this trip back in May this year on the Jewel of the seas first outing, they are all very nice ports and you are right you will be able to do it all yourself. We had to pay about 4 dollars each for the shuttle bus in a couple of ports, but the port tourist busses go to all the sights if shopping's not your thing.
Our fave port was Gurnsey, my husband wanted a very expensive watch from a jewelers which was inland, we had a couple on our dining table who were from Gurnsey and they said to take the bus it only cost 50pence (they didn't charge us going as they were running late). We then walked to the little chapel, it took about 20 mins (we passed in on the bus on the way to the jewelers). The chapel is so sweet and is an absolute must to see. There are a lot of underground stuff to see from the war years that also sounded very interesting, again these can be reached by the local bus service. We took longer to get round in the town area as there was 3 ships in that day.
Have a great cruise, we just got off the Constelation yesterday from a trip round the baltics, so I just came on the boards as I was feeling depressed and needed a cruise fix.......
p.s. forgot to say we've also been on the Aurora, oceana sister ship, the food is the best we've ever had on any cruise they will look after you well.