My first exposure to Animorphs was with my oldest daughter, then in 5th grade. I like to read or at least skim what my kids read, to know what’s going into their brains, so I read her library copy. It was, IMHO, a younger version of the classic sci-fi model, using a fantastic/futuristic setting to approach big moral/ethical questions.
That particular Animorphs book started my daughter thinking seriously about what constitutes just war. While she was interested in them, they proved good fodder both for discussion between us and for her private contemplation of larger concepts. I was rather pleased with the ideas it sparked and the direction of her thoughts.
What, specifically, is your husband concerned about? Has he read any of the books, or is he just generally worried about the genre?
-mary