I got a pair of these Tourmaster Air Tracker Mesh pants with a removable liner this summer. I got them at cost so I couldn't refuse them.
http://www.tourmaster.com/xcart/catalog/Tracker-Air-Pant-p-292_4.html-they are fairly cool even on hot days
-will fit over jeans or other pants
-have adjustable waist straps for the "mature" fit

-liner comes out quick with velcro tabs
-you can take them off over your boots by just unzipping the legs
-the bottom legs will unzip which will convert them into shorts if you like
-the armor is only in the knees, not in the hips but for the price I like them.
-grey is a little more forgiving in the sun then black I think