When it comes to one off events (such as Open Evening) I use Guidebook to build a mobile app to support the event. The free account gives access to most of the features and enables you to have up to 200 downloads on the App – so far I have not had an event reach this limit.
The site uses a fairly easy drag and drop method to build up the app, which can then be published to Windows, iOS and Android devices. You can include a schedule for the event and a “What to See” area to list features (in my case areas of the school which are open for parents to visit). You can also use it to link back to Social Media, such as Facebook, Twitter and YouTube. The result is a professional looking guide produced in a relatively short amount of time.