Thanks for advice on telling my son what to do in emergency -- very helpful.
Other answers:
How did you explain things to the boys?
Not much explanation, just that Mom had taken medicine that knocked her out more than she thought it would.
What is their relationship with their mom like?
They love her and are close with her. She can be a decent mom when she's "ok".
How are the boys doing? Do they see a counselor?
They do not. At the moment they seem truly fine, so I'm just not sure when is the right time / way to get them help if/when they need. (I'm a big believer in therapy, having done it myself for decades.)