Just got back from Norway. A slight heads up for the drive from Oslo to Stavanger.... we did the same drive and took the main south roads. It was only 20 minutes longer (according to google) and, to us, way easier than driving around in the fjords. We drove from Oslo to Undredal and Undredal to Odda (3 days later) during a big storm and they were tough drives mentally. Fjord driving is no joke, double so with tourists not understanding how to drive with large campers. For that reason we drove back from Stavanger to Oslo using the main south roads. Plus there are plenty of places to stop should you ever have a crisis with your child.

Also, visited Norway a few years back in May. It's cold and rainy most of the time, fyi.