I'd think some time spent wandering around a wrecking yard looking at door latches would be worthwhile. I'd think you should be able to trip two latches with one solenoid, just need two rods from the mechanism out to the latches.
James - '62 Ranchero (200cid), '71 LeSabre (464cid)
The ONLY safety device we need is a 6" sharpened steel spike bolted to the center of the steering wheel of EVERY vehicle.
Emergency Rooms and Funeral Homes will be busy for a week or so, then I predict a dramatic drop in vehicle accidents.