My mom is retired, receive monthly SS check & small pension. If I pay her to providing care for my son will that impact her SS check & pension? If not what's the max?

I'd like to leave my son with my mom when my wife and I both go to work. My employer have a FSA Child care option that I can put as much money into to pay for this service. Childcare is not cheap so for us this is an option that we are considering but would not do it if it negatively impacts my mom's monthly SS check & small pension.

Thank you in advance for your help.

Chip