I'm sorry but there's no way that 3 toddlers alone are not deemed at risk whether the law says it or not. Risk doesn't just mean intruders, it means fires, emergencies etc as well. My friend in college had a ten year old sister and mum worked two jobs so his sister was home alone from 3.30-6 when my friend got home from college, but she was 10! A 10 year old is capable of understanding what to do in fire, who to phone if there's an emergency, not to answer the door etc and this was in her own home. Not a foreign country that she was unfamiliar with.
The *risk* in question is the fact that they were toddlers incapable of dealing with a situation if it arose.