Our experience at 2 PG events: Pitchers will normally pitch 2-3 innings. Playing time rotates around, but all of the players bat in a constantly rotating order. If you're on deck at the end of one game, you lead off the next. Players will get to play their primary position, but can also get into others if they're willing. My son recently played SS, 2B, LF, 1B, and P during 3 PG games. (if a spot was vacant/available, he jumped on it...)
My impression is that for defensive purposes, more attention is paid to the rounds of infield taken; the games appear to be more about looks at pitchers. I'm sure defense is noticed, but the focal point of the games seems to be on the mound.
Hope this helps.