Yavapai is in a great location. Be sure to go the main lodge for lunch or dinner. Pretty awesome views.
Personally, I would recommend that you drive west from Lake Havasu and stay overnight at the 29 Palms Inn. This place has been a favorite getaway for us and the Thodys and Hollywood starlets for many years. Plus, it is located on the edge of the Joshua Tree National Park.
Here is what Peter wrote about it.
Here is one of Megan's articles about itIf you do stay there -- EAT AT THE Pool restaurant. The owner is a Michelin Chef and his food is awesome and not at all what you might expect.
Hmmm. There's not much to see anymore at the Dinos at Cabazon--they are still there, but they have been swallowed by neighborhood homes.
I have never been to Six Flags and usually when I am passing by there, I am going to someplace else and have never really explored that area. Except for some off-highway explorations. i will do some cogitating.
Mark