Madrid - Seville - Ronda - Toledo - Rome - Chinque Terre - Florence - Venice - Vilnoss - Milan - Paris - Mont St Michel - Loire Valley - Paris - Rotterdam - Amsterdam
In that order :)
Trip of a lifetime, you'll love it. Ronda and Toledo are both particularly spectacular in their settings and if ever there is the opportunity I would add Segovia and Cuenca to the itinerary for the fairy tale alcazar and cliff-top hanging houses respectively. I hope you have a wonderful time, I think it would be impossible not to! I bet the family's excited.