Instead I want to set up one test machine for users to try it and ask THEM if they like it.
This experiment will have a predetermined outcome: the users will not going to like it (if they even bother to try it) because its is different. Don't do it unless you realy need an excuse not to transition to linux.
If I were you I would do a gradual change:
- 1. Before you do anything else, do your homework. Make sure you can run everything you need for your business on linux. This means checking with everybody and his sister in the company and going over every single app and document that is being generated or used. Put your findings in writing. Develop plan for the transition, that includes a pilot transition of small number of desktops. Show your findings and your plan to the management and make sure you have their approval in writing.
- 2. Start the pilot by transitioning only the PCs with the now obsolete windows XP. Do it one at a time, allowing enough time for the main user of the machine to transition, while he/she has your full attention. Use this to iron out any transition problems. Stuff like compatibility issues between file formats and software. Leave the newer windows versions that are supported as is, but start gradually adapting the users to the free software they will have to use on linux (switch MS office to Libre Office for example, but keep the windows OS). This way the shock of the transition and the backlash will not be as bad.
As far as distro's come, the obvious choice is to do it with the distro that you are most familiar with. Alternatively use a distro that will be supported for years to come, even if you are no longer with the company.