I think your plan is excellent. JB Weld will work for sure and I was going to mention (but you already knew it) to drill a small hole at the ends of the crack. I say go for it, I'd do the same thing.
BTW, you could also use some Bondo if you had some laying around. A bit more flexible than JB.
I bring up the Bondo only because I had a 4 x 4 wood post that I discovered was damaged by termites on one side, about 1/2" deep. This post supported a patio cover. I was going to jack up the patio and replace the post when a buddy said, "clean out all the termites and rotted wood, fill it with Bondo, smooth, and re-stain". I did just that about 10 years ago and the post is still as solid as the day it was new. Moral of the story; termite hate Bondo.
Doesn't relate exactly to your situation, but you get he idea.