Would i be an a-hole for telling my bestfriend her husband cheated onher

I (28f) have a best friend let’s call her Kelly. She is married to my husband Tim’s (30m) best friend Edward (32m)they are married and have kids together. My husbands sister Katie has known Edward her whole life as Tim and Edward have been friends since high school. Back in 2019 Katie came from out of state to visit and hung out with all of us. When Tim and I were heading home Katie was suppose to go with us but elected to stay the night at Edward and Kelly’s house so she could babysit their child the next morning as both Edward and Kelly had to work. The next day we picked her up and went about the visit no issues.

It is now 2022 since then Kelly and Edward have had 2 kids and everything seems well until back in march I was planning a surprise party for Tim when Katie called me to tell me she wouldn’t come to her brothers party cause Edward would be there and she can’t be around him. Confused I asked why and she stated back in 2019 when she visited they both got drunk in the basement and had sex while Kelly was upstairs sleeping. I was shocked. Katie came clean to her brother Tim about it and since then we have both sat on this information. Tim talked to Edward and he confirmed that it did happen and that he regrets it. Tim asked if Edward would ever tell Kelly and he said no he’s taking it to his grave. My dilemma is I feel like Kelly has every right to know the situation. And on top of that if I plan a family gathering for a party Katie won’t come if Edward is there and if I don’t invite Kelly and Edward she’s going to know something is up. On top of all this my husband and I have gotten into arguments about what to do with this info so it’s also affecting my family. And every time I see Kelly it’s weird for me knowing this info when she has no clue. I’m planning on telling her soon but I worry that I’d be an asshole for breaking a marriage and ruining the lives of not only my best friend but her 2 children. So would I be the asshole if I told her?