Long term job in the afternoons taking care 2 children 8 and 10 years ol

We are a family living in the center of Madrid (San Bernardo area). We would love to have a native english student willing to work with us afternoons from 5pm to 9pm (Monday through Friday). That person would have to pick up the children at a nearby school, accompany them to their extracurricular activities, bring them home, help them with their homework, showers, keep the house decent, etc. till we get home. 

It is a real job from September 2019 to June 2020 (both months included) and we ask the person who comes to take it seriously. This includes university exams periods, that we know could be tough, but we could not afford not having anyone appear.

We offer a fix salary of  500E a month. 

If you are interested, please contact me  so we could schedule an interview somehow.