If there was a serious emergency of any sort then I'm sure he'd remember to tell you.
'He forgets stuff, no matter how important ,he forgets.'
Yes perhaps, but my point was that if it was an emergency or something that was essential for you to know, he is perfectly capable of understanding the importance of the situation and telling you immediately. Not in two or four hours, by which time he's forgotten.
so imagine:
OP texts 1 hour after lunch: What did the DCs have for lunch?
OP's ExH: Cheese sandwiches
OP texts four hours after lunch: What did the DCs have for lunch?
OP's ExH: Um, I'm not sure, ham sandwiches maybe?
Who cares, and why does it matter?
ExH phones OP IMMEDIATELY: DC has fallen off a swing and broken ankle and we are going to A&E.
There we are, you see, he hasn't forgotten, because it's important enough to warrant immediate contact.
Look, your children are old enough to understand that their father has a medical issue and they are old enough to know if he's feeding them too many aspirin or whatever, and to be a bit vigilant where it matters. Many children live full time with parents who have far worse issues than this and they come out relatively unscathed.
Either lighten up and put some trust in him/them and stop the controlling/infantilising of him, of if you genuinely believe his problems to be so severe that the children are unsafe in his care then you should rethink whether he should be having unsupervised access AT ALL.