Arena seems to like Donavan as a forward when he has the full squad. This allows Reyna to play as attacking midfield. As the team matures (read Reyna gets older) he may drop Donavan into that spot. He has played 5 at midfield bringing Donavan back there then. Mcbride sits up at top alone when he does that. I'd take Wolff over Ching because of the experience and the hustle. He made things happen in '02. (Also I watched him play at South Carolina) Dempsey and Quaranta are midfielders and may be going - depends on how the European players look. So, I'd take McBride, Donavan, Twellman, Wolff, and Johnson.
Adu has had his 15 minutes of fame (yellow card) at the National Team level until after this WC. And he's locked into the US squad - can't play for Ghana.
My humble opinion.