Um, totally disable the power button? I don't think so...

But, you can enable the "Soft Poweroff" power menu item by editing a system file called systemui.xml (a search will tell you how to do this).

Soft Poweroff is different from "Lock Touchscreen and Keys", because to bring it out of Soft Poweroff you have to hold down the power button for a second or two to wake it back up instead of just a click. (also, Soft Poweroff puts the device into offline mode, saving even more battery life).

Maybe this'll help?