How much to pay for a school pick-up?

[Sammy]

My neighbour will be picking up my 4yo at school once or twice a week. I want to approach it as a purely commercial transaction so need some advice on how much to pay her.
My daughter goes to a different school than her kids; it's on the way to her kids school - but may be some back and forth as timings differ.
She doesn't need to take her to activities and can just go along with whatever her kids are doing.
One day will be pick-up at 5 at afternoon club, and I will then be home at 6 and the other day
pick-up at 3 and then spending 3 hours with them until I'm home.
Thanks