Are you going to be traveling or stationary? If you stay in one spot maybe you can sign on with a local internet service provider. If you are traveling, you only options are to pay for what you go over or accept what wifi is available at the parks where you are staying.
It has been hashed, rehashed and then hashed again who or what is at fault for the internet service at campgrounds. Regardless of whether it is just plain greedy campground owners, incredibly stupid campground owners, evil campground owners or even the remote, outlandish possibility that unlimited speed and bandwidth isn't available everywhere, the fact is campground wifi isn't likely to do what you are describing. You will almost assuredly have to provide your own service if you need to stream movies and use the internet for business.