If you are now considering an all inclusive, which I think is wise with your group size and the fact that you want to do 3-4 dives a day, then you might want to consider Case del Mar. I have not stayed there myself, but I know lots of groups your size like it there and it is well priced. They also have shore diving, but I can't speak to it. I think their website is horrible and not the easiest to navigate, but you should add them to your list of potential alternatives: Home | Casa del Mar | Cozumel, México