Just around the corner from Holywood Palace, and in the shadow of what when finished will be the new Scottish Parliament is the Dynamic Earth, a geological/ natural history attraction that manages to be interesting for both children and adults.
The show/ tour is a walk though about eight to ten different displays, each dealing with a particular period of the earth's geological history starting with the creation of the earth, development of continents and going through the development of life and it's evolution into its current myriad forms. Later displays deal with the importance of conservation and man's responsibility for the planet.
If you are anti-conservation, you may find this bit a little preachy. But it is thought-provoking.
If you are a creationist, don't bother at all. For everyone else with kids this is highly recommended; a good value activity. A tip: your hotel or tour bus or people in the street may have flyers for cut price entry.