Look good in a casual relaxed way that won't look out of place in a bar, and select comfy clothes with minimal/zero chance of wardrobe malfunction. Your presence represents your husband's good taste in women to his friends --- this is your one "job" in this trip.

Look interested (attentive body language) when they have a conversation and be a supportive listener --- that's all you really need to do, to make them think highly of you, because good listeners are so rare.

Make encouraging noises to keep them talking (especially if it's about a topic that's completely alien to you). This can actually help you learn new things so you won't feel like you wasted your time listening to things you don't understand/can't apply. Nobody will notice you are "boring"/have nothing to say if they're too busy talking, I promise.

Only talk when you are asked a question, or if they want your opinion. If you've been a good listener, they will want to hear what you have to say, for any time you have something to say. Men are generous when they feel respected.

If you have nothing to say, don't say anything. Use the time to catch up with personal relaxation and enjoying a change of scenery. If you're chill, people around you will pick up on the cue to be chill too.