Rather than converting to a twin 50 amp service, you might consider running one of the air conditioners on a separate 20 amp line. Most RV Parks have both 20 amp and 30 amp services available at the campsite.
Removing one of the air conditioners from your existing 30 amp breaker box, and wire that into a separate 20 amp box with a male outlet plate. The park's 20 amp breaker will provide the circuit interruption should something short-out. I would recommend that you use a 12 AWG extension cord for the separate air conditioner.
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