drewman

Hello, I'm new here, and wanted to get some insight from other parents on an issue that I've been having with my stepson. I am his mother's 3rd husband, and have no kids of my own. Stepson is 22yrs. old and has a girlfriend of the same age. They got pregnant last year, and had a beautiful baby girl. My wife and I are semi-retired, and volunteered to move to the state they live for 6 months, to babysit 5 days a week at no charge. This allows them to both work and earn a dual income, and bank everything. Babysitting their adorable child has been a joy for my wife and me, and made the past months fly by.
Earlier this summer, my stepson and his girlfriend announced they were getting married. They got a ring, his girlfriend picked out a wedding gown, and chose her bridesmaids. They put a deposit down on a catering facility. They did all this with their own money, and we were very proud of them. After they told us about everything, I wanted to help out, and gave them a substantial cash gift so that they could have the wedding they otherwise could not have afforded. They accepted the money, and were very grateful.
Everything seemed to be going well until last week. My stepson told his girlfriend that he did not love her anymore, and the wedding is off. She is in total shock and completely humilated. My wife and I are in agony having watched this happen. At this point, me, my wife, stepson and girlfriend are the only ones who know. He does not want anyone else to know right now.
Personally, I think this is terribly inconsiderate because many other family members and friends are under the impression that the wedding is still on. They have begun to ask us questions about all the events surrounding the wedding, and we have to bite our tongues and make excuses for my stepson. I really really have trouble with this. It is causing a lot of friction between my wife and me, because she believes it is none of our business. I disagree, and say we are enabling his selfish and disrespectful behavior.
To top it all off, it is my opinion from an etiquette standpoint, that since he cancelled the wedding, I have the right to ask for my cash gift back. He has not said a word about it to me, and seems like he is not going to. My wife told me not to say anything, that he has more important things to worry about right now. I don't get it....is a stepparent just supposed to give everything they can to their stepchildren, yet not have a say in anything at all, or ask any questions?
I do understand that children of divorce have a rough upbringing, and they often take the attitude with parents like, "hey, you messed up my life, so I'm entitled to behave this way". I want to confront him, ask for my money back, and give him some suggestions on how to conduct himself as a mature responsible adult. My wife and I are arguing constantly about this, and it's tearing away at the fabric of our marriage.
How should I handle this? I'd really appreciate some insight that parents here could give me. Thanks!