If two parents do not have an autosomal recessive trait, what can you say about their children?

The children may or may not exhibit the trait. It depends if the parents are carriers of the trait or not. If they are both carriers, the children will have a 25% chance of exhibiting the trait, a 50% chance of being carriers, and a 25% chance of not having the allele for the trait at all. If only one parent is a carrier, their children will have a 50% of being a carrier and a 50% chance of not having the allele. If neither parent has the allele for the recessive trait, their children won't either.