I agree, $5.00 is probably what I would charge.

Really think about it before you take them on though. It's a long day already, you're going to make it a half hour longer. That means, dinner is a half hour later, cleaning is a half hour later, homework, baths... they all get pushed back.

Just make sure you're being realistic. There's nothing worse then commiting to someone then wanting to take it back 4 weeks later.