I don't really like the check/calls. They aren't telling you whether he's bluffing or value betting you. Does he have air? Possible he has AA and is just hoping you dont have a king. It's possible he has AK as well, so I'd throw in a check raise on the turn too. It's gonna make him think hard about his hand, unless it's a bluff. As Geanossss said as well, checking when trips turn up, and then calling screams "I HAVE TRIPS BUT IM SLOW PLAYING THEM." Personally I'm always betting this flop, unless I know the player behind me is super aggressive and will bet for me.