I've heard of parents doing this with math homework and having their kids do the challenging math that the parent is afterschooling while the parent does the inappropriate / unchallenging math homework. I don't think there is a shining correct option because the homework isn't appropriate.
Perhaps one thing to be aware of is how your child feels about you helping and passing off your work as his own, especially as he gets older. Is this a slippery slope that will make it easier to order papers off the internet instead of writing them himself because he already knows how to do it? I'm really asking not judging. Also, adults often do have to do work that is boring. At what point/age do you teach a child how to do the work when he is bored out of his mind? Is being in a classroom day after day enough to teach this? I've contemplated this as it is a "skill" that can make or break a budding career. Currently, I have a child who views homework as handwriting practice, which she loves, so this isn't an issue for us yet. I think it will be at some point.