I took my family to a Reds game on Tuesday 17th. We had seats directly behind 3rd base and 7 rows behind the outfield end of the Brewers dugout. That end of the dugout happens to be where visiting players leave the field between half innings.
Both of my sons (at different times) went to the rail as the Brewers were leaving the field and Prince Fielder tossed each of them a ball.
Even better was Josh Hamilton autographing the balls after the game. He was signing near the Diamond View seats for everybody who wanted an autograph. Needless to say, my sons had a great time!
Also, if you can get a parking pass for GABP garage, I highly recommend it. You park your car and walk right onto field level.