I think that was me. Also, I posited that maybe Tylee was on edge, and deliberately kept herself and JJ away from the dangerous edges.
I think that's possible, certainly. She had reason to be on edge, and for some time.
I also suspect that one of the murderous trio was lucid enough to realize that any "accident" that happened in a high-profile place was likely to attract significant attention, investigative and otherwise, and that accidents involving not 1 but 2 children (because there couldn't be a witness and either surviving child would have been deeply traumatized and, in TR's case, probably suspicious) and thought better of the plan if plan there was.
In the event, their backup plot was similarly flawed, but like Patrick Frazee in Colarado, they might have been genuinely surprised that anyone in JJ or TR's lives would care enough to make a fuss about their disappearance (because Lori didn't), or perhaps they trusted in their own powers of deception, which had served LVD pretty well to that point, or simply pushed ahead because they wanted to and figured their chosen-people faith or loved-upness would carry the day.
I don't see Chad, LVD or AC as being particularly gifted strategists or long-term thinkers. And whether they were genuinely mission-led or cynically focused on wealth and pleasure, they were working with clear timelines under some pressure, as the move to eliminate Tammy seems to show.
As I catch up with this case I grow more convinced that these were very dangerous people, who would have gone on killing as required, and were absolutely capable of recruiting more soldiers to the cause. It's easy to see the anodyne and even ridiculous figures of Chad and LVD as they are now in jail, and the circus that seems to surround them, and look past the threat they presented at the time, but I find this to be one of the most chilling of the cases I've followed here -- so much cruelty, so much harm, for so little. IMO.