TeamViewer v9 to TeamViewer v15 Upgrade Path

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We've got roughly 100 TViewer v9 computers and 15 users that I'll need to upgrade to TViewer v15. What's the best order to do these in?

Should I have all of the users upgrade to TViewer v15 first and then upgrade the individual computers (That's my plan right now)?

Most of these 100 computers are pure remote devices where I won't be able to be sitting in front of them. What's the best way to do these? Right now I'm thinking about deploying another temporary remote access solution; do the upgrade; then remove the temp solution.

Thoughts?