You can run all three on the 50 amp service. As explained above, there are 50 amps on each leg, or about 6 KW per leg, 12 KW total.
The start up amperage is around 30 amps for a couple of seconds, and the 50 amp breaker can handle a 200 amp load for 2 seconds without tripping.
Each unit should not be drawing more than around 12 amps, and if one is on one leg, the other two can be on the other leg, so max 25 amps on one side, 13 on the other. Your battery charger, refrigerator, and other appliances will work fine on the 50 amp service.
However if you are in a park with 30 amp max, then you will be restricted to only 2 of the A/C units if EVERYTHING else is off. If you have a residential refrigerator, then you could run one A/C and the refrigerator can cycle on and off, along with other loads. The residential refrigerator is probably about 3-5 amps load.
Good luck,
Fred.
