6-7 suited in MP

I would just call here. You don't want to run into MP3 with a very strong hand and cap it shutting out the CO, BB, UTG, and UTG+1. If you are absolutely convinced it will not get capped, you absolutely should 3-bet it, but I think a call is fine here.

Please note that this would be totally different if you had JTh, where you would be raising and reraising with overcards to go along with your OESD and backdoor flush draw. 8 cards give you the nuts instead of just the 4 outs. You could still hit a 10 and run into QJ.

Besides, if you hit a 5 or a 10 on the turn, you can check raise MP3 and trap all those players in between for a big bet.