You should definitely stretch in addition to any exercise you do. Stretching is as important if not more than just about any other exercise. It is what will keep you young.
I don't know about the cardio bike. As for basketball and baseball, you might want to add in some light workout focusing specifically on the muscles you use the most in those sports. Basketball, there's nothing you can do to alleviate the tired legs. The things you can do to not hurt worse is build up your leg muscles. Doing light leg workouts on days you don't play basketball helps a lot. As for baseball, just building up your core should sustain some of the pounding. And yes, stretching is a must before...as for stretching after, just do a walk around a track or on a treadmill, drink a lot of water, and let your body slowly get back to "normal range".
