Disclaimer: I am not a lawyer. The information below is general in nature and should not be taken as specific legal advice. If you have a specific legal question you should consult an attorney practicing in your jurisdiction that is familiar with the law and case history regarding the issues you wish to address.
The following general information is based on the assumption you are located in the United States or a country with similar intellectual property laws regarding the use and licensing of photographs.
Would this be commercial usage of a photo?
It'd be a gray area. It would hinge on whether the photos were presented as the people in them endorsing someone else to purchase a ticket to the next event or presented as a report on the last event in a separate story from a solicitation for potential attendees to purchase tickets to future events.
The fact that your organization is a non-profit has zero bearing on the issue. If persons are depicted as endorsing a product or service, even in a solicitation offered as an opportunity to donate to a non-profit, then it's commercial usage. Period.
But that's the least of your worries.
The real issue is whether publicly releasing the photos in any way might be a violation of their right to privacy while in a private place.
If there's any doubt at all in your mind that the people depicted in the photo might not want their likenesses used to publicly represent your organization, then you need to get their explicit permission to use photos of them in writing, with the exact nature of the intended usage spelled out in the written release.
The fact that you even asked this question leads one to think that you already know some of them might not want their likenesses used. Get signed releases.
You've been a bit obscure about what type of activity goes on at your private social club. Some private clubs engage in activities that many members do not wish to be made public. This may or may not be applicable to your specific case, but you've left some doubt in that respect. Editorial usage of potentially embarrassing photos that serve no public interest have been ruled to be defaming, even when the images were taken in publicly accessible places.
This concept is illustrated in the classic case of Daily Times Democrat vs Graham which has been used as a landmark case in many subsequent cases since 1964. It's also almost universally cited in various photojournalism textbooks in the United States.
For a fuller discussion of Daily Times Democrat vs Graham and another related case, Raible vs Newsweek, where a man did in fact sign a photo release but then sued and prevailed when his photo was used to illustrate a story that implied he held views and made statements that he neither held nor made, please see the later part of this answer to a related question here at Photo SE.
Both of these cases involved photos taken in public. When photos are taken in a place considered private, the bar is set even higher. Get releases!