I think I am going to go with the full suit, but the only problem is the single vent, I do have a fairly large backside and the vent does open a bit. If I don't button you can't really tell, but what would you recommend?
Tie without jacket, especially on a guy our age, is a no-go. You'll look like you're trying too hard, and you won't appear as confident as you will in the jacket.
Vent issues... they don't drive me crazy. If your suit fits perfectly except for the vent, you might end up with the best-fitting suit in the room. If your suit fits okay, with some vent problems and one or two little issues, then you'll still be fine. Nobody expects us to have perfectly fitting clothes.
Who and what is your audience?
Have you visited the museum before and noticed what everyone is wearing?
If you are making a presentation, are you selling yourself or anything connected to what is being presented? If so, then dress up one notch above your audience.
Your apparel may be different in Montana than in New York City.
(In my opinion, I suggest not going with just the shirt, as it reminds me of a used car salesman. The suit, for me, would be much better in a professional presentation - unless you were going to a low end Montana museum )
All my best,
Then it is similar to interviewing for a job - whereby the principle is to dress for the job you want to obtain, and not to dress for who you are at present.
Your credibility is being presented along with the facts of your presentation. And how you look will play a part in how the judges will vote (Style and Substance).
Your audience knows people, and if you aspire to get hired in the dream job you want - even as an intern - then dress the part.
Board Members may also be present. Here is a link to the Board of Trustee's page of the museum (including pictures of how they dress):