now if Vito had said "I want all inquiries made, but no acts of vengeance," then it would make more sense.
I believe that is exactly what Vito meant.
I want -- all inquiries made. I want no acts of vengeance. I want you to arrange a meeting, with the heads of the Five Families. I want all inquiries made into the killing of my son, but I DO NOT want any acts of vengance taken because I must make the peace here. I must find out who my real enemy is, and make sure that I do not lose another son but instead get him back home safely.