I don't mean to bring into question anybody's parenting skills, but Unsound seems to have the perspective that kids are incapable of being taught restraint, respect and just plain good behavior.
As I said, I have a four-year-old who grew up with my system and now have twins who are going through toddler-hood and there's never been an issue. Granted, I would not want my system to be a hazard to them - so the tube cage stays on, the speakers are bolted to their dedicated stands which are filled with sand, etc. To think that you'd have to "tether" everything to the walls as Unsound suggests would indicate that you've got some bigger issues to contend with than top-heavy speakers.
Furthermore, I'd really hate to think that it'll take "luck...and...a couple of years before they can be reliably taught to respect adult toys." Parenting should be more than protecting children from themselves and accomodating them to the point of allowing them to run our lives. There's a hierarchy in a family and children need to be lovingly taught where they fit in the family structure. And here's a hint...It's not at the top of the pyramid.
As I said, I don't mean to offend anyone, nor bring into question their parenting skills. I'm just trying to offer a bit of perspective based on my real-life experience(s).
You can have your system and responsibly raise your children, too. Now...whether or not you'll have the time to listen to it is another matter altogether ;>)