I'm generally skeptical about horror movies with children in them.

Rating: 9/10 (23 December 2018)

The writers usually give kids unbelievable dialog and/or they aren't really up for the task, but no one wants to be too critical of their performance so you can't know beforehand. In Bird Box they were very young.
In this movie the kids don't have very many lines. Mostly they're just getting lectured at by Bullock as she tries to warn them to keep them safe, but I was more than pleasantly surprised with the result. I don't know if it was more the writing or their acting (especially the girl), but for me they were both totally believable, and it made my heart ache for them.
Their roles were only a small part of the total movie, but central to the development of the main character.
Overall, I enjoyed Bird Box a great deal. It's hell being right all the time, especially in a horror movie.