Agree that offline areas are a must. It's helpful to set up predefined Map Areas ahead of time, to make the download process much easier for new users.
Be aware that once you have a map set up and people are using it, you can't make major changes to the map, or the layers themselves, otherwise syncing will fail. If a change is needed in the map, it's generally easiest to create a new map (copy) and tell everyone to download the new map, sync any edits in the old map and then delete the old one.