I was just looking at a video of the grand villa and honestly I think even 12 adults would be all right especially because, being adults, you can come and go more at your leisure so not everyone is necessarily leaving or coming back at the same time. It might be moot, I don't know if the OP is planning a party of 12 adults or 12 people of different ages and sizes.
But at the same time, consider the space that you do have. Would you be planning big ol' get together "home made" dinners where you'd need a giant dining room? Would you be planning a movie night that requires a media room? Are there so many little ones in your party that you need to tackle them all in one room it-takes-a-village style?
It might be better to try to book a 2BR and a 1BR. You won't get the grand dining room or the media room. You'd only get 3 toilets total instead of 4. But it would use fewer points total than the grand villa, it's still a decent amount of space, and you'd get 2 laundry facilities instead of just one, and for a group that size, that might be even more important than the extra toilet although YMMV.