traveling with 2 and 6 year old to London, Bergen, Stavager, Geiranger, Olden, Flaam

Does anyone have any specific recommendations for things to do with children in London, Bergen, Stavager, Geiranger, Olden and Flaam? We already have tickets on the Flaam railway and my son really wants to see Platform 9 3/4 at Kings Cross station, and I was wondering what else you would recommend with young children. Thanks so much. We are traveling in early May so the roads to the fjords may not be clear in Geiranger.

In Bergen, your children might enjoy the funicular up the mountain. They may not be wowed by the views, but you will be! Near Bergen, you can visit an ancient stavkirke. The children probably won't be much interested in the religious or historical aspects, but the church is fascinating in itself. It's tiny and full of carvings and fanciful architectural features--very much like something in a fairy tale.

Hyde Park has a lovely path to walk around the pond and the glorious Princess Diana playground would be my first choice to spend a chunk of the day enjoying London. For sights, a boat ride down the Thames and the London Eye are in the same area, near Big Ben, in which case St. James park is a great place for the kids to be able to run around.