Consider the following, not as essay questions but rather like headings on bulleted lists. What a good invitation needs is the facts, short and sweet, the most important things, that everybody already knows, all swept together in one place, for easy review and action.
What is the "purpose" of this particular meeting/workshop? And for what time period? What qualifies as "action" and what is required in an "action plan?" If the purpose is not "action" then what is that "purpose"? Vision? Strategy? Structuring? Support? Healing conflict? What kinds of things will be accepted as successfully satisfying the "purpose"?
What are the best things we've ever done in this group, that have any connection to the "purpose"? Are they recent enough to be held up as examples to be repeated or exceeded?
What are the current conditions that matter? Survey data? Anecdotal data? Priorities? De-prioritizations? Current crisis? Upcoming changes?
What are the things we know we want/need to do/have/create now or next? What activities must be created or continued regardless of any current crisis, conflicts or shifts?
Who are the people needed to get it done? How soon can they clear the day(s) needed?
What resources and supporting structures are available to leverage? Coaching programs, communications tools, internal facilitators, volunteers, meeting spaces, budgets, etc.?
What sacred cows, "dead mooses" and other lines are not to be crossed? What is still unspeakable or immovable here?
When will we meet, and where? (days, times, location(s))
When will we know that this process is really working? In the meeting? After the meeting? One month later? Four months later? Next year? Next survey? And how will we know... at each point?
What documentation is required from the meeting? Who will use it? Who will distribute it and to whom? Will it be the beginning of a longer record, a formal report, or a one-time announcement?
What support and resources are required for the most important change(s) desired to actually happen? If not available, can they be acknowledged? Invited? Created in the working sessions of the workshop?
What else is going on the in the world, in the community or organization, and in individual situations that seems to matter now?