Agreed. No matter how benign the conditions are, there is no way a 4-10 index player can break 100 on TP, or any of Open courses in the current rotation. (Maybe Merion just because it's quite a bit shorter. A sub-4 index MIGHT break 100 if he has a career day, driving it long and putting well.
Add the pressure of live network TV, celebrities, etc. and I would bet the farm that these guys don't come closer than, say, a 105. I expect there will be some penalty shots and at least a few "tap-ins" that are missed under the pressure of the day. That assumes they REALLY play the Open tees, rough depth and green speeds. If they wimp out (unlikely) on the setup then it's more achievable.
Still, it will be fun to watch. Everyone loves a train wreck (i.e.NASCAR) and will especially love to see the celebs getting beaten up.