this hand is a lot easier if you make a small raise on the turn. This way you either take the pot away from 5-x and straight draws and save yourself a bet on the river by finding out if you are against a 6-x hand now, and probably for cheaper.

Still, once MP calls behind you on the turn you have to check the river. It seems likely that he is holding a 6-x hand or a missed straight draw (at casinos i have not ran into many players who understand betting aggressively with trips to force out draws, hence they frequently slowplay them). Also, i think you are going to have to put in one more bet either from BB or MP on the river -- BB if he has a 6 or MP if he has a 6 or is bluffing his missed draw. It is a difficult spot and you save yourself a headache and money raising the turn.