This concept works great with my little Jeep trailer. You can see from the picture that the parking brake handle moves a mechanism that pulls a cable to a splitter and then pulls another set of cables to equally expand the shoes while parked. This little setup works great on this application but I cant imagine why you would need mechanical or electrical parking brakes on the Airstream?!
I use the expanding wheel chocks between my tandem wheels and they work great. A wedged shaped block would do well too
If you do consider electrical, the current draw to maintain contact would suck batteries down in no time. If you decide to go forward with the plan please post pictures so we can see the final project.