The Fedora Multiboot Guide
Should be easy to setup, make sure you set grub's timeout to 10 seconds or so, shorter timeouts can make it difficult to choose an OS before it goes to the default. You might be able to remove the default and force the user to choose from a menu of options.
Bob my workplace has a number of people I'd describe as computer idiots, including some managers. You need to make it easy for the dimmest users. We have one guy who is in front of a touchscreen with a numeric keypad 40 hours a week and has yet to figure out it's the same format as a telephone, which he's been using for more that half a century. He practices the "Hunt and Peck" technique for for finding numbers on the keypad, forty hours a week for over a year now.