The old Territorial Prison in Yuma is very interesting and worth the stop. Anza-Borrego Desert is also pretty nice and you might want to check out the Salton Sea since youll be close.
Other places to consider are Texas, along the gulf coast, New Mexico where its not quite as warm as Arizona but often considered a well kept secret. If you guys are urban folks and love restaurants and theaters, Phoenix is probably a good bet. If you...
If I were you, Id stay in Oregon as the gas prices are a bit cheaper. In Brookings there is a tiny RV park called Apple Hill, and its 55+ so I don't know if you qualify, but its nice and close to the ocean.
We travel cross country about every other year to see the grands and have done itjust about every season. If I were you, I would I'd leave mid Sept when all the kiddies are back in school and take the northern route there. Hwy 2 is fine but I'd take ...