Best Pet for travel?

We travel with two dachshunds, one Dalmatian and our baby Boston terrier. Not all at the same time, though. Usually two is our max. We have live in help that takes care of the other two that stay home. All four travel well, and enjoy camping. The two left behind howl piteously until we've driven out of earshot. We have another dachshund who prefers no travel, ever, so she stays home. We will lose one of the dachshunds soon, though. She has end-stage congestive heart failure. We keep upping her meds, but soon it won't be enough. Poor girl was seven when we adopted her from the animal shelter. She will be lucky to see twelve this spring.