You can daisy-chain the kegs. I've never heard of anyone doing it here, but we used to do it all the time when I worked for Pepsi. Gas into keg one, Keg one out to keg 2 in, keg 2 out to serve. Keg one fills keg 2 as you serve...
That way we never had to worry about blowing a keg at fairs/festivals.