What schedule do I use to report cash money I receive for watching my granddaughters who are both school age while my daughter works?

You may not need to report the payments as income to you.  If your daughter does not claim the dependent care credit on her return then you do not need to report the income.

 

If she does claim the dependent care credit then you can report the cash income in the "Self-employment" topic under the "Wages & Income" tab.  

 

Here is a link with more discussion on the topic.