The Sportsman will probably weigh around 600-700 pounds, the Kawasaki around 500 and the two dirt bikes will probably weigh around 200 each so you will be way under your 3,000 pound capacity. However, you need to figure out your hitch capacity and try not to exceed that. There should be a sticker on the hitch telling you the hitch capacity as well as the total capacity, 3,000 pounds. I'll bet you will be ok, but you should check anyway.
2012 GMC 2500HD D/A Crewcab
2012 Jayco Eagle SuperLite HT 26.5 RLS
2009 Crestliner Superhawk 1900
2013 Polaris Sportsman 550 EXP
2008 Polaris Sportsman 700 X2