So we checked out the book, and we love it. Of course, we have had several conversations with Owen about what another name for a donkey is, but we love the story, and the illustrations are fantastic.
So I feel like we have a good handle on when it is appropriate to say the word "jackass". Like, if we are at the zoo, and we walk by the donkeys, it is ok for Owen to say "Momma, there's a jackass." Or, when he is playing with the donkey stuffed animal from the Democratic National Convention, he can say to Willett, "give me back my jackass." Cautiously, I agree that that is acceptable.
With that said, we read the book last night at bedtime. That and a Dr. Seuss, a constant in our house. Owen seemed satisfied with his books, also being exhausted from the Parade of Lights. With that, it's lights out, hugs and kisses all around and a tuck-in routine for the night. As I turn off the light, Owen says to me, "goodnight, jackass."
Lesson learned.