we are moving cross country next year, and stuck on the best way to transport our three seniors (one dog, two cats). Flying them in cargo isn't an option. I think we're gonna have to trade in one of our tiny cars for something bigger.

Hijack Santa's sled

Car is about the only way. You could rent an SUV, it will cost a bit more and you will have to pay a drop fee at the destination, but it would be better than buying a new car if you really do not need a new one.