Windows with Open Office and Mozilla will train the users to use this software and when the change does happen they will know how to operate Open Office and Mozilla under Liuux. The price is right, virtually nothing, to use those software titles, just be sure to have them donate something to Mozilla.
What OO needs is an Outlook and Access clone, or work-a-like. I suppose Evolution can handle Outlook's function under Linux, but Access is hard to match with its ease of use database. When I had a small business, we developed a lot of databases in Access, so our old clients would have to have those databases and apps based on them converted to something else.