Caretakers stand and wait for infant to complete idles

Ah, yes. I've seen that in my game too. I've learned that when one Sim is standing around doing nothing, then I probably told that Sim to do something with someone else, and I need to cancel whatever that other Sim is doing. Sometimes it's something I told the other Sim to do, but sometimes it's an idle action that they started spontaneously. Especially when childcare is involved, it really makes no sense. Two twins could be talking to each other and starve to death by preventing their parents from feeding them.