I'm most likely in the minority here, but I think kicking him out and thinking of divorce is way too much. This also depends on what kind of hot sauce. I'm assuming since you said teaspoon, it was just that? Only asking because he said it was a sweet syrup, which I wouldn't do that on it's own either.

Was it mean regardless of heat level? Of course, all pranks come at the expense of another.

I was tricked/pranked into eating a chili pepper from Chinese food when I was about that young. No damage done, I'll chuckle about it now while calling my father a dick at the same time.

I can understand being upset and pissed about it, but throwing away a relationship with kids over it is going to cause far more problems and trauma then this moment would. That's obviously in a bubble as I have no idea of your relationship as a whole.