Q. Is the old sash my son was given by his godfather acceptable for his wear?
A. I am so glad to hear that your son is lucky enough to be in a family with a Scouting tradition. I certainly understand the importance of the matter to you. Once an item is an official part of the BSA uniform or an official piece of insignia of the Order of the Arrow, it may be worn, even if it is not the "current" uniform or insignia being sold. Once it's official, it's always official. Since your son was given an Ordeal sash by his godfather, and your son remains an Ordeal honor member, he may wear the sash, no matter how old it is, as long as it's presentable.
Let me suggest that he reserve his godfather's memento for ceremonial occasions. Then he can use the Ordeal sash from his own ordeal for work crews and service projects, and times in his OA life when he may get it dirty. A godfather's OA sash is a priceless gift, and it would be a shame to alter it through the good work I hope he is doing with his lodge.