Yeah, I've praised restraint as one of The Witch's best attributes, and I'd apply that to the fate of the twins as well. We've seen the fate of others - the baby,
And not knowing it presents a different kind of horror than showing it, which in the context of that point in the film, was very effective.
Kalib, the dog. The twins are gone and it's not going to end well for them. We don't need an info dump to know that.