Take you kid out to the ball field. You stand were you might be standing as you shoot and get her to walk the bases as you make some test shots at each base and at home. Then get her to do the same in the outfield. Then go home and look at your shots. You may not even need a tc. But if you do you will then know by just how much you want to grow. The tc14eII, tc17eII, and the tc20eII are made to work with your lens. Light should not be a problem with a 2.8 starting point. With a bit of pr work you might sell prints to the mom & dads to cover the cost of your new TC if needed.