Ok. I worked for the Canadian government for a while.
When they say, blazer and dress slacks, they mean your sharpest blue blazer and your best, pressed and clean, dress slacks. In conservative tones, such as mid grey, light grey or dark grey.
I once was called up in front of the entire department, made to stand and was critiqued because I had worn, "jean like pants" to a day at work, on a "casual" Friday. I was told, very bluntly, by the department head that I was to wear a full suit every day, a proper topcoat over that outside, dress shoes at all times except when in transit and a tie. Casual Fridays meant that I could wear an odd coat and dress trousers with a necktie. It definitely didn't mean jeans, and once in a while I'd get an email at 8PM on a Thursday (we were tied to our Blackberries, expected to answer even if at home within a reasonable time) saying "Friday will have XYZ visiting, so it will be full suit and tie".
I also got notes on the blackberry at 3PM saying, "You all can go home. Have a good early weekend", so it wasn't as bad as it sounds.
You should have more stressful things to worry about than what you are wearing.
I would wear a simple blue blazer with a white dress shirt, no French cuffs, pocket square, tie pin or lapel pin. You have the option between a red and blue striped tie or a blue tie with a subtle pattern. Do not, do not, wear a bow tie. Your goal is to blend in as much as possible. The first guy to wear a bizarrely coloured or patterned suit is like the first guy to quit clapping at a North Korean rally. You don't want to be that guy
I was asked once to stand up and tell my bosses a bit about where I came from. All I could think of was to say that I took honours at a MUN conference, nothing about my education or why I was qualified for the job or even what kind of volunteer work I did. I was so nervous, I couldn't even figure out what to say. I should have expected the question and made a proper speech. Luckily it was in front of two supervisors, not the entire office.
When you are called to introduce yourself, say, "I'm Jim Johnson, 38 years old, graduate of Yale with a degree in Public Policy and a minor in Government Relations. I'm married with three kids, I just spent the past ten years working for Wallace and Wallace as a policy advisor. I hope to bring my experience from my studies and my experience in my prior activities to support the department and my co-workers.
A listening meeting is just that. Don't jump in with allegories about tennis, professional wrestling, golf or gardening. Don't say things about what your kids asked you, and for sure, don't tell a joke.
C.