The maximum rating covers the loads that the truck's components can handle without rapid wear or damage and from the numbers your Yukon will be OK.
Something that is an unknown is how long it would take to stop the trailer using only the Yukon's brakes should something go wrong with the ones on the trailer or the brake controller. I found this out with my Chevy Tahoe and it took a country mile to stop with a 3500 lb. trailer load. After that experience I stopped using the Tahoe to tow this trailer load.
With your infrequent trips and very low miles involved there is nothing to worry about. Get the weight distributing hitch and a good brake controller (if your Yukon did not come with it as part of the tow package option).
A backup camera is also a good add-on.