I think you should drop in without telling them and then bask in the awkward silence that will inevitably follow. Of course I'd prefer that they get it together and stop making assumptions, but as long as they're going to make assumptions and you don't get the accommodations you need I think any resultant schadenfreude resulting from their embarrassment is fair game.
@arush I suspect this one is just a panel discussion with researchers. But, since I don’t know what it is, I don’t really know until I get there. I’ll just assume. Besides, they have my LinkedIn profile. If they can’t figure it out from that, it’s their problem.