New to the forums...but I did want to add my two cents on this topic, as I just recently found THE solution. I went to a RV show in Portland Oregon, and found a booth called WiFi In Motion. www.wifininmotion.com This appears to finally be the answer to everything I've ever needed for Internet access while on the road. It essentially is a kit with everything I needed (cellular antenna, 3-watt amplifier, and a wireless router).
Now, my wife can be browsing the web in the passenger seat, and the kids can be on their laptop in the back, all while I'm driving down the road. Pretty slick technology!