Just a suggestion: Tint all the windows.
The rear windows on 03+ Expeditions are 'smoked' for privacy, but do little to nothing to reduce UV rays, radiant or infrared heat. Have a window tint place put a layer of film over every piece of glass, windshield and moonroof included. If you don't want or like dark(er) windows, or if its a legal issue, look into 3M Crystalline film. Its perfectly clear but will drastically block heat and UV rays. Your skin, dog, and interior will thank you. Lower interior temperatures mean less AC time is needed, but the other benefits are much greater.