The voltage may be OK with one AC but none of us can say for sure. It depends upon the AC size plus other loads, the AC voltage at the plug under load and the quality of your extensions and especially the plugs.
The safe sure route is to have the electrician install adequate sized wiring for a plug within reach of the single RV plug. And at that point you should consider installing a 50A circuit which will handle all of your current and future needs.
Yes I know it will cost a lot more but then you've covered all bases.