Originally we decided on no more than 40 people. But we are up to 60 now and hopefully (fingers crossed) we don't go over that number.
I think choosing AI or non AI is completely a personal choice. For our group, AI was the best way to go. We are a bunch of party'ers so I didn't want my guests to have to be worrying about their bank accounts while on vacation if they want to drink and eat and do certain water activities. I also like the idea of us all staying together because this will be the first time we've (his friends, my friends, his family, my family) all been able to hang out in the same spot since everyone is all over the country.