If he has special pins that he loves and doesn't plan on trading I would encourage him to leave them home. Even if he doesn't plan on trading them they can fall out of the bag, or as I hate to say may get legs and walk if someone else likes it. I had a few of my pins "walk": when I refused a trade I didn't think fair. The next thing I know they pins are gone.
I have some of my favorite pins hanging on cork boards that I bought in the stationary section of
Walmart. I painted the cork to match the theme, most of them are black, but my Figment pins are on purple and my patriotic are on red,white and blue.
I hated wearing my lanyards especially when it got warm. If I had a shirt with a collar it was ok but with a t-shirt the lanyard rubbed and irritated.
I would also recommend he get some kind of small bag to carry his trader pins. I bought mine at WDW about 6 years ago. It is 4"X6" and has a strap but I usually put it on my fanny pack. If I am going to look bad with a fanny pack I might as well look really bad and have a pin bag attatched. I haven't seen plain ones in the stores but have seen princess ones. I am sure he doesn't want that.
You could also make your own with a small makeup bag that you put felt or foam pages in for his pins. just use a piece of foam for the pins then a sheet of felt for the divider to keep them from scratching each other. I had a makeup bag that I bought from Walmart when I started collecting pins way back in 2000 that was a perfect size and didn't look like a makeup bag, it looked like a small notebook.