Did you want your users to be able to use their own blogs as well, with a separate one for your team? Or do you simply want to disallow users from posting blogs, and your team can post them?
If it's the latter, you can go to yoursite.com/admin/users/roles, then uncheck the permission to create blog posts for members. Leave it checked for your team. Then to set the blog as your home page, go to yoursite.com/admin/pages and drag the "Blog" page to the first position on your main menu. You can rename the label to something else, such as "Home".