Or maybe I should just keep my mouth shut.
Going on and on about your grownup children is one of the prime ways people act old. It’s not the fact of having adult children that makes them seem old, it’s talking as if their kids are the most interesting thing about them. As if their children are the ones with the noteworthy lives now, as if their own lives are beneath mention.
So mention that you have kids, by all means. Say what they’re up to, if you’re asked. But don’t make them your main topic of conversation.