Groups lack free/busy status in Microsoft Entourage
When you want to invite a group to an event, you should realize that Microsoft Entourage does not display the free/busy status of its members. It displays "No Information" rather than appropriate free/busy status.
The only workaround for this problem is to individually invite each person to a meeting. You can invite more than one person to an event in the same way you would send an e-mail message to each person individually. Also, Groups cannot be expanded in Microsoft Entourage, so you cannot see the members of a group to check the individual free/busy status of its constituents.
This is different from Microsoft Outlook on Windows, where the combined free/busy status of a group is presented when you are inviting a group to a meeting.