My husband and I are planning a road trip for next summer. It will be my husband, myself and our three children. (Ages 9, 7, 5) We were also considering taking our dog. We will be leaving from St. Louis, MO and going to Crescent City, CA. From there we will go to San Francisco, CA to Grand Canyon Village, AZ and then back to St. Louis. My biggest concern is space in the car. We drive a 2011 Mazda 9. Does anyone have any advice on storage? We don't want to attach a trailer and so we were thinking maybe something that can go on top of the car to keep luggage and such. Also, any other advice or tips would be greatly appreciated! We are so excited!

Thanks!