Part-time Nanny For 3 Kids, Long-term Option

We are looking for someone reliable and trustworthy to help care for our three kids around 3 days/week. We'd prefer to hire someone consistent, who could make at least a year long commitment. Dad's firefighter work schedule rotates, so the days he has off are not always the same each week. We do know his schedule for the year, but overtime days are not known until one week in advance. Mom starts school in August (Mon-Fridays, but will also need to study on weekends). On the days Dad works, we are looking for someone to pick kids up from school and be with them until around 8/830 p.m. We'd like someone responsible and caring who could help with homework and prepare basic dinners. Our two girls are pretty independent, so most of the "babysitting" would be for our 4y/o boy.