Some daycares want an hour but I tell them 30-40 minutes is much better with the shorter attention spans.
Themes sometimes depend on the time of year, especially Christmas,Halloween and end of the year celebrations. Otherwise they often just want a "fun show". You can create a show based on almost any theme and send it to them. I am working on an idea now for a storytime show for daycares.
Family events are not often held at daycares (at least around here) but there have been a few Christmas family celebrations, particularly at Montessori school.
Hope that helps some.