[Dire]

There is exactly one hand you can be afraid of in this spot: AsAd. Our passive guy isn't betting KK on this flop into 4 people and he's probably not raising 66/77 UTG.

Outside of that you have AQ/AJ - both would play the exact same way from a tight but stationy type guy, especially if their kicker was a heart. They'll pay off here sometimes, sometimes they won't. But checking here because you put your opponent on exactly AA is just seeing monsters under the bed, and refusing to accept money that's being handed to you.

If you're going to be so nitty about it, make it $50 on the river. He'll always call with his AJ/AQ then, and again - he's not going to bluff you on the river. But I think he calls $100 often enough with AQ to make it more profitable.