Hi J.,
As the last lady stated, you are doing something when you are babysitting if even they are sleeping. The babysitter is there for reassurance that everything will be ok and if anything does happen they will be able to address and fix the situation. You might have to raise your rate because the average rate for 3 children is 15 dollars.
Just my opinion (I have been babysitting for 14 years, was an assistant director in childcare and have met all the certificates and qualifications for babysitting.)
Hope this helps,
E.