Wow, that's a bad situation. Obviously, I would not bring such a dog. I wouldn't stay at that party with kids either. I don't mean to be morbid, but as much as I love dogs, there are bad ones that need to be watched and I will not be around a bad dog without a solid knife on my belt. The knife serves two purposes. The dog will sense my confidence to defend myself and will not attack me, and if the dog goes after someone else, I can stop him if necessary.
The family member in question is a bit callous about other people and doesn't quite seem to get that this is unacceptable. Sounds like several people are going to get together and flatly tell him he's not welcome to bring the dog next year. This event takes place once a year, lasts a week, and requires everyone to drive several hundred miles to a shared set of vacation cottages. Changes are not made lightly, which is why no one said, "get that dog out of here!" and just put up with it. They're pretty tolerant in general. The fact that they're discussing this at all says a lot. I'm not sure they would have, if the dog hadn't bit a second person. I like to complain about all of Mrs. Silvercrest's relatives, but unfortunately this guy is one of mine.
It's a Newfoundland. big, strong, loving, not to bright and love the water. they've also been used as rescue dogs.