What would you do?

Here's my story:
A little background. This happened the year before Covid. I was 48 at the time. I'm no supermodel but after 3 kids, eating healthy, yoga and run in a few 5k each year. I can still wear a size small bikini. I'm also a leggy 5'9". My husband is two years older and we hike together and still maintain a healthy ** life.
We rented an airbnb at the beach with our long time friends Bill and Gina. Bill is very tall and good looking for age 60. Gina's mom is Asian and her dad is white so she looks very good for her age.
After unpacking my husband and Bill decided to go bourbon tasting so they got an Uber. Gina want to go shopping and she also had tickets to a concert that night. I didn't care for that type music or shopping to she went solo. I changed into my bikini and went to the beach to enjoy the sun.
My husband and Bill came home around 4pm. Good thing they took Uber because both were buzzed. We sat out back together while they worked on one of the bottles they'd bought. I was having wine and feeling a buzz. My husband started nodding off in the recliner so Bill and I took him to our bed and he was out for the night.
Bill has always been flirty but this time he turned it up a notch. He told me my long tan legs had him hard. I noticed the tent in his shorts. I finished another glass of wine and the next thing I know I was sitting on the railing and he was standing between my legs. He pulled his ** out of his shorts and with a joking tone said, "I'm showing you mine. Are you going to show me yours?" I playfully pulled my bottoms to the side and watched as he pressed the head against my entrance and enter me. He started going in and out slowly for a few moments. His next words were, "I guess I should stop because I'm about to finish." I've had my tubes tied and I knew he'd had a vasectomy from past conversations. I said, "Well, we've went this far. Go ahead and finish." He slowly continued until he started finishing. We never kissed. We just waited till he finished and went soft. I made the mad dash to the shower in my room. He went to his room and showered. We came out and talked like nothing had happened for another hour or so. Whew!
I went to bed with my alcohol smelling husband and Gina came in very late.
The next day by husband had a hangover and Gina slept late.
After 24 years of marriage and 3 years dating, this was the first time I'd ever had ** with anyone than my husband.
To this day, Bill and I have not talked about it and thankfully things are not awkward. Thankfully he's never hinted about doing it again.
I plan to keep this a secret forever and tell no one.
However, I also no regrets and proudly admit that I would do it again.

What would you do?
Keep this a secret or tell your partner?