Yes, if I were to use a legitimate form for grooming it would be a person manipulating or tricking a child into doing something sexual with them and that being the end goal, only sexual satisfaction.

The definition as is used currently could be applied to all romantic relationships regardless of age, which is why it is merely used manipulatively.... grooming people to view child sexuality as non-existent and paedosexuals as abusive sickos.

As for my example, that was just what got me into researching the word. From the article the family did seem to just use the kids as sexual toys and nothing more. They used sex toys were just part of the abuse, I think the term "grooming" was just thrown in there. I know a couple preteens who could have benefited from the use of a vibrator so they stopped using their electronic toothbrushes (I was told about their toothbrush adventures by them). Which would be, as you said, from the child's own wants and interests. Though there is nothing wrong with introducing something to a child to see if they are interested.