Second AC on the garage!

[2014Fuzion300]

Ok, I know there is a lot of topics about second AC units, however my question is a little different ;-)

I got the camper four months ago so I have not tried it in the summer yet...
But a lot of people complain about how "hot" it gets in the garage area. Even with a 15000 BTU's .

My camper is at the dealer now (fixing minor bugs), and I got a call from the service manager saying that they are running some "specials" on AC's
My camper is 30 amps and if I add a 13500 BTU's I have 2 options:

1-Tap to existing 30 amps system and not been able to run the two ACs at the same time.
Or
2-Run the cables to the outside of the trailer to a bracket with a male receptor. This way I can plug to 120 volts pedestal in the campgrounds.

So the question is:

What do you think is the best system? Price wise is the same.

The option to change to 50 amps is not for me because is to expensive.

Please let me know If there is something I'm missing !

Thanks for the input !