Make sure the trailer roof is capable of supporting the weight of the second A/C. Just because there is a 14x14 hole there for a vent fan, doesn't mean it has the support for a heavier A/C unit.
Some campgrounds frown on using two receptacles, such as plugging in your 30 amp shore cord and then another heavy cord into the 15 or 20 amp gfci receptacle in the pedestal. Many campgrounds won't care and probably won't even notice.
Charles
'03 Ram 2500 CTD, 5.9HO six speed, PacBrake Exh Brake, std cab, long bed, Leer top and 2008 Bigfoot 25B21RB.. previously (both gone) 2008 Thor/Dutchman Freedom Spirit 180 & 2007 Winnebago View 23H Motorhome.