Is fixed focus 85 heads suitable for children's photography?

85mm is still a little far. If the child is your own, it's not a big problem if you are obedient and cooperative.

If you are taking pictures of unfamiliar children, you will be nervous if you are too close, and you will not attract their attention if you are too far away.

35~50mm lens is easy to use, the whole body background and chest circumference can be used, and you can also cut large photos.