Passing down a keepsake like a wedding ring is a wonderful tradition. Tell the others to get a life.
He could wear it as a necklace and the ring could be tucked out of sight and not be a cause for scandal.
Such a thing would only be necessary if the mere act of wearing a ring was actually the sin of scandle. According the Angelic Doctor, the sin of scandle occurs in two ways:
1) when a man intends, by evil words or deeds, to lead another into sin
2) when a man commits an act that, by its very nature, leads another into sin, even if the man did not so intend
I don't see how the mere act of wearing what amounts to a family heirloom falls into either of these categories. There's no evidence that he's intending to lead anyone into sin by wearing the ring, and I do not believe that anyone can honestly say that the act of wearing a ring does, by its very nature, lead anyone into sin.