Not all browsers support every feature in Google Documents. Not surprisingly, Google Chrome does support all features of Google Documents and Google Drive. For that reason it is preferable to have all participants in your training sessions use Google Chrome. Google Chrome automatically updates whenever a new update is released by Google. A day or two before your training session send an email to all participants asking them to install Chrome if it’s not already installed on their laptops.
If getting all participants in your training session to use Chrome is not an option for you, at the very least stress to them importance of having the latest version of their preferred browsers installed. Not only is this a browser security issue (older versions of browsers are more susceptible to security threats) it is a Google Documents functionality issue. The latest versions of browsers support the most functions of Google Documents. For example, as of this writing Google has officially ceased supporting Internet Explorer 8.
Finally, regardless of which browser you ultimately have participants in your training sessions use, have them all use the same browser during your training session. Initially, this might be uncomfortable for some participants, but by the end of the day most people will be comfortable with a different browser. Having everyone use the same browser will make your day easier. When everyone uses the same browser if there are unexpected glitches or problems they will likely be the same for everyone in your training session. Solve the glitch once and you’ve solved it for the whole group for the day.