Izturis should play 2B everyday over Kawasaki. Izturis holds a career OBP of .331 which isn't spectacular, but I think it is better than what Kawasaki could do. Plus we owe Izzy 9 million.
As for Boni, I ultimately think we trade Davis at the deadline and Bonifacio takes his place as late game defensive replacement and pinch runner.
Sending Kawasaki down right now made the most sense. This way, we don't lose any players. Plus I think it will take him time to adjust to playing 2B.
I wouldn't be surprised to see Kawasaki back with the team in a couple weeks once AA makes a trade.