Since you are so limited with your time you can best take advantage of this combining drills. The more skills you can combine into one drill the better use of your limited time. Every week your practice should include elements of ball handling, shooting, passing, defensive footwork, rebounding, and team offense and defense. Here might be an example practice. Team that scores gets to keep the ball and run a half court offensive possession.
Good defense resulting in a score is rewarded by extra offense.
If you need conditioning, have the losers run extra. Shooting contests are usually a good idea because you get to practice shooting under pressure late in a practice when you're tired. You can help yourself a lot by meeting your team a half hour before their 1.5 hour practice time, and have them do some simple isometric exercises to increase their body strength and stability. This age is probably a little young to be doing any extreme amount of weight training, however basic muscle tone and strength can be significantly improved through isometrics. Do you stretching prior and after practice outside the gym.