Honestly, I think that Eric Young is only cluttering your options at the moment. Your best lineup, with your roster the way it currently stands, would have Bonds at DH, Berkman in leftfield (3), and Klesko at first base.
Torii Hunter is going to be horrible for you. He might save some runs for you, but he certainly isn't going to put many on the board. I would look into either getting a cheaper defensive player for that position, or seeing if Vernon Wells is available. He's also a 1 in center, and hits lefties well, which is something you need.
I would try to add an R2 to your bullpen, whether it's Armando Benitez or Neal Cotts. What that means is that I don't care if you get a stud or just an arm to throw at the back end of your pen, you're gonna need someone to eat some innings to keep the rest of your guys fresh.
Estrada won't help your defense one bit, but his OBP will be huge in your home park. I think your lineup could be very productive if you get lucky on the rolls for some of your lower OBP guys.
Dave Bush will be eaten alive by the Shea team. Just a thought.
Hope this helps a little...