Netflix on iPad questions?

So I am driving to another state tomorrow and I want to use the Netflix app on my iPad for my son to watch. My husband. Has a Netflix account already so I can just use that but I was wondering if while I am driving Netflix eill be using the internet because I will get charged extra for Internet use so can i just use instant queue and it not be using the Internet? Because while I am driving there will be spots that don't have internet and I don't want it to pause and buffer and things so can I just use Netflix or should I just rent movies off of the iTunes store?