Well, the best way to do batch updates is to use limit and skip and run it say 1000 at a time. I would ideally run this for a few times on a test environment before doing it on prod.

The other way is to create a new collection afresh and once it has run to completion, rename it. Even in case of failure, you can switch back to the old collection instantly.

That being said, it looks like a fairly simple update to me. You're just updating one field based on some condition, I don't see a lot of risk here.