Searching English Native Speaking Nanny/Teacher (Barcelona)

Hello, We are looking for a native English speaking nanny for our two children (5 and 8) in Barcelona City to improve their English. Pick them up from school Tuesdays and Thursdays, from 5pm to 7.00pm. School is ten minutes walking from home. Preparing a quick snack for them and playing with them. Our children are fluent in English, although not native speakers, so we want somebody with creative ideas to entertain them, imaginative enough to develop a new game every day and somebody that put emphasis on teaching new English vocabulary and expressions.  
We are looking for a long term relation. 
Many thanks and best regards, BEATRIZ