You can do Dragon Beaux in the evening- and nail hotpot and dimsum at the same time.
If your BIL is coming from Toronto/ Vancouver, I’d suggest skipping Cantonese. I don’t really know how Chinese food is like in Montreal. If its anywhere else, then Cantonese/ dimsum may not be such a bad idea. Dimsum especially if you don’t have a large group of people.
I was trying to book Jai Yun a couple of months ago but was told that the chef was on vacation and that he would decide Jai Yun’s future when he returned. If the chef decided to keep going, then it may be an interesting option.
Or, maybe chain together a few restaurants for a full day Chinatown crawl?
Hon’s-Chongqing Xiao Mian- dimsum, GG Bakery, and finally back to Z&Y/ R&G for dinner.