'Tis the season most homeschool parents start perusing the curriculum fairs for next year's picks. Most of the time my "hunts" were successful once I had figured out what I liked, what my kids enjoyed, and what I could stick with from year to year.
A writing curriculum I can highly recommend is Institute for Excellence in Writing. We use it in our school, and the co-op uses it as well (at the high school level, I believe). It comes with videos, writing samples, explanations, and more. As easy and fulfilling as I find writing, it's the hardest subject for me to teach and the one that takes the most time investment to do well.
This curriculum is designed for either the teacher who has a basic idea of how to teach writing or for the one who has no clue. If you know what you're doing, I recommend using a few of IEW's built-in source material but mostly your own. I believe in doing "double duty" with history and writing, or literature and writing, or science and writing. In other words, if you are reading about Louis XIV, find some source material about him to gear the writing assignment toward. (Okay, that was a poor sentence, but I shall go on.) If you're studying about moles (either the rodent or the skin type), it's easy to adapt with IEW.
I recommend previewing the first few DVDs before teaching your kids. Get the material this summer and do it during some down time. Once you get the hang of it, you can simply watch it with them (provided you decide to use the built-in source material).
My two caveats:
1) Don't let your kids become "formula" writers. This curriculum is heavy on 'dress-ups" ("ly" adverbs, who/which clauses, adverbial clauses, preposition openers). That's fine if your kid always starts sentences with nouns or pronouns, but using anyone else's style too much will hinder a development of one's own. I'm all about giving your writing a "voice." Your voice, not your teacher's, not your best friend's, not your favorite author's, and certainly not the voice of everyone else in the same writing class. You want to avoid "ese" of any kind. I also prefer strong verbs over "ly" adverbs. (Which one is better? "She bit her fingernails and tapped her watch as she waited for the 1014?" or "She waited nervously for the bus." ?) I am trying to break my students of the habit of putting an "-ly" adverb before or after every verb. It's overkill, but they've been trained on IEW.
2) Prepare to groan a few times through the video teacher's corny lecture style. I have no room to talk, I know, but have you heard the line from "South Pacific" about being "corny as Kansas in August"? That's Andrew Pudewa.
Check it out. Since you can use it on multi-levels, it's a worthy investment. Since the materials are built-in as well as flexible to your own, it's a double-good investment. As for the humor factor, that might kill the deal for ya.