Thanks for all the responses!
Cats can be good traveling companions if they're ok with cars. It helps to introduce them to all types of new experiences when they're young. Kahlua has always been a good traveler. We got her from a shelter when she was about a year and a half old. Selina has taken to it just fine, since we've had her almost from the start. We've made a point of taking her with us everywhere it's ok to take a cat. She likes going to Lowes with us and riding in the buggy.

Getting a cat used to a harness and leash takes some patience. You start by just putting the harness on them at home to get used to it. They typically spend the first few trials trying to back out of it, or just flopping over on their side and acting like it's killing them. They eventually get the hang of it. Then you get to do the same drill with the leash. Kahlua has walked miles and miles of trails with us on a leash. She can't walk quite as far now, so she gets carried more.
I'm no cat expert (or spouse or child expert for that matter), but we've had pretty good luck with the cats we've had. You just have to figure out what works for yours.
:):)