The question is rather, whether you have control over this 'tweaking'. Many shops apply some general tweaking for the common holiday / wedding / birthday party / whatever family snaps. But this could be a) not what you have in mind or b) counteract what you have done to the pics already. So best is to talk to these people and advice what they could do or should not do. Not sure whether the cheap neighborhood print shop will do this. I heard from a friend that KT Colour is one of those shops where you can discuss the details before printing. Triple D does test prints as well.