Just relocated from NY to TX, drove 1850 miles in 3 days, 600 first, 700 second and 550 the last day. I really have to say I enjoyed every mile in it. Not uncomfortable at all, and had one dog on my passenger seat, seat all the way back, and the second in the footwell. I did stop every 2 to 3 hours mostly for the dogs to get some running and food, as well as giving them anti nausea pills (1/3 each). they were totally fine and most of the time just sleeping.
I looked into shipping first, but no regrets driving it down south.