Unless I'm mistaken, as soon as you assign someone as the delegate of your calendar, you're giving them FULL access. The permissions tab greys out because it is no longer necessary. The person you assign as the delegate will also get meeting invitations for that calendar.
Now, as for everyone seeing everyone else's calendar, this can become tedious (unless someone knows of a better way). Basically, each calendar that you want shared has to be located on the mail server (not the hard drive). In other words, if you use PST files, you'll need to copy the calendar out to the server directory which is usually called "Mailbox - Username" or "Outlook Today - Mailbox - Username".
Then, you've got to add permissions for each individual. Right-click the calendar, go to properties, then go to the Permissions tab. You have to do this for each calendar and add each name. You get the idea! Maybe someone else knows a better way for a long list of people.