A little bit of idle time on the engine to get it reasonably warmed up before putting a strain on it isn't going to hurt anything and in my opinion helps the engine. Note that I did not say you have to let it sit there and idle for thirty minutes to bring it up to full operating temperatures.
A little bit of idle time to reasonably warm up the engine is best if you're going to pull out of the RV park and immediately up onto the highway and have to merge with traffic. Look at it this way, you're engine will spend far more time idling at stop lights than you'll ever idle it before starting out in the morning.
Bill