In English, child can mean a young person, but it can also mean something like “offspring” or ”progeny”—i.e., it can denote the relationship that one has with one’s parents. For example, it is entirely appropriate for my parents to say something like “It makes me happy to see all my children together again during the holidays.” This usage is not restricted to parents, either; one can purchase self-help books for “Adult Children of Alcoholics” and the like.
In German, I have been unable to find similar usages of the word Kind or Kinder. Is it ever appropriate to refer to an adult as a Kind? If not, how would, say, a German father or mother of grown-up children express a thought like “I would like my children to visit over the holidays”?