Well, wanting the extra space for the dogs certainly makes sense.

Moving is stressful, no doubt about it, but I think you can relax a bit when it comes to the roadtrip portion of it. You shouldn't need to make reservations for this trip, so as long as you are giving yourself enough time to comfortably make the drive - and have a day or two extra available, just in case you do hit bad weather and need to sit out and let conditions improve - you really shouldn't have too much to worry about.