I agree with LTL, wear the black suit, and a fabulous shirt, then if you feel too dressed up you can take off the coat and dress it down. maybe even untuck it. I don't think you'd want to be caught dead in the Charles Hotel without a suit on. You never know who you'll run into there. If you hang out at the bar, you might meet Ben Affleck or something. You'll want to be looking you MOST fabulous.