Part of the group is too noisy for the host's comfort. If Grandma wanted to change this, how should she go about it? I assume she can ask people to keep the noise down. Could she also ask them to stop drinking if that seems to be the underlying reason?
I think the group going to the basement
is the way they, and Grandma, are dealing with the noise level. Grandma could throw a dry event if that's what she wants, but the fact that she hasn't yet gives me the impression that she doesn't actually mind the drinking, she just has trouble hearing if she goes down there.
I guess I'm just sad that there are cliques in my family. So much so that you can see it when you sit down to dinner - there are multiple tables and you can see that some members just won't sit and talk with other members. Same thing with our summer reunion - certain family members are not spoken to for the entire time they are there. The whole thing just makes me sad, but I guess that's what happens in big families.
Do you know the reasons for these "cliques"? Are the people grouping together closer to each other? Do you know why people are being excluded? There may be underlying reasons that you're not aware of. Big families tend to have very complex dynamics and more secrets than you might think. I'm the middle grandchild out of 14 and was shielded from family interpersonal drama until very recently (I'm 26).
This is a good point--and also just that it's super hard for a huge group to all converse together. For example, any time I've been out to dinner with more than about 5 or 6 people, the conversation will split. And at big family gatherings, yeah, they do tend to spread through the house after dinner.