Cunard offers a shuttle service every 15 Minutes to downtown (next to the city hall) where all the shops and main attractions are located. Excellent public transportation in the entire city. No need to buy an expensive tour. All attractions within walking distance.
Hop on hop off Bus stops right in front of the ship. City hall is 5 minutes from the ship (by foot). City center not more than 10 minutes by foot. Oslo offers excellent public transportation (e.g to Holmenkollen ski jump stadium)
STAVANGER (not on your port list)
Ship stops right in the middle of the city. all attractions can be easily visited on foot. Mini Hopp on hopp off buses offer a city sightseeing tour for those who do not want to walk. suggest to visit the oil museum (not more than 10-15 min by foot from the ship). Old twon with over 100 preserved wooden houses is just next to the pier.
Very small town at the end to the Sogne Fjord. Main attraction is the railway to Myrdal. Visit the railway museum which gives you an idea how this railway line was built. Good information on the train as well which stops at a very nice waterfall for picture taking