Here are some notes.

The scheduling system automatically figures out if the current user is the leader of one or more of the groups (??or individuals??) listed in the attendees list, and if so prompts with a confirmation that asks if the meeting should be penciled in on those users' calendars.

I'm thinking that we may want to keep it simple here and only allow pencil-in when meetings are scheduled for registered groups. So here's a plausible rule: in the confirmation dialog, the following information/questions are included: (1) You are a leader of the following group(s) whose attendance you've requested; do you want to pencil-in for them? (2) You do not have pencil-in authority over the following user/group calendars: ... ; do you want to send email notices announcing the meeting to these users? (3) the following individually listed attendees are also in one or more of the listed groups: ... ; the pencil-in or email notice will be done only once for these users.

Also note that the dialog for scheduling a meeting is quite similar to scheduling an appointment. In particular, the following fields are exactly the same in both dialogs: Title, Recurring, Category, Priority, Location.

2.5.1. Simple Case

Sketch: show a scheduler going through the process without encountering any difficulties. The steps are:

1. The user requests a meeting to be scheduled for a range of possible dates.
2. The system responds with a list of possible times in that range.
3. The user selects one of the possible times and confirms the meeting.

In this detailed case, show the scheduler encountering some difficulties, and having to adjust scheduling options.

2.5.3. Changing and Deleting Group Meetings

Basically, the same rules should apply as for individual meetings (see Section 2.4.6), but with the wider-ranging consequences of having to notify all participants.