I think we will reluctantly have to get it in. I don't think the button is slowplaying all that often on this flop, since it should hit both your MP opening range and SB cold-calling range extremely well. Slowplaying just wouldn't make sense for him, since he can expect at least one of you to connect relatively hard with this board. It is more likely that he picked up additional equity on the turn with a hand like 3456 or 6789, or maybe something like AA3x/AA2x.
SB could still be slowplaying a set, but he's also fairly short and might have decided that he has enough equity to get it in 3way with his pair+openender type hands.
Overall, I think we have enough equity against their ranges to call it off in this spot.

what about checkingcalling turn? Seems like villain either picked up a wrap here with AA32 or something; or a similiar hand to yours.

Yes, I think once I've bet the turn and the action went like this, there is no way in getting off this hand. The question really is if betting turn is better than c/c. I felt like it is because I was expecting both players to have missed fairly often (whereas I'd happily call of SB's shove) and the BTN to rarely ever raise besides some exceptional cases like when he improved with AA55 or slowplayed KK. In the overwhelming majority of the time I felt like I'd just let 8 cards see a free river if I went for the check and therefore preferred betting over checking.