I'm not sure that they would help you plan but rather to show you what to expect when you get there. Personally I think you should find plenty of info on the Internet and none more so than at The official N.P.S site for the parks. Use the map to navigate your way around the parks you may want to visit and you will find lots of visitor info on each one.

Like I said earlier, you can't really go wrong with a nice sized comfy car for practicality and cost, but it really is down to the individual.