There are 7 sacraments that give grace, and things called sacramentals that do not give grace. Why do I read in my Church bulletin about classes being offered to prepare people for "sacramental marriage?"

Well, in your bulletin “sacramental” is being used as an adjective, not a noun. Hence it is not wrong to speak of sacramental marriage. But, your bulletin could be clearer by saying “Sacrament of Marriage (or Matrimony).”
 
That said, your distinction between the nouns, “sacrament” and “sacramental”, is sound. Sacramentals include things like blessings, blessed objects, holy water, medals, etc. They bear a resemblance to the sacraments. But sacraments, as “efficacious signs,” absolutely confer the grace they announce, presuming the recipient is properly open to receive them. Sacramentals are signs that prepare us to receive grace, and dispose us to cooperate with it, but are much more dependent on our disposition to be fruitful. More at the Catechism of the Catholic Church (#1667ff).