Nanny or Personal Assistant?

Hi, I have been working as a nanny for almost 5 years. I know a few personal assistants in the area and they do basically the same job I do, but get paid at least $5/hour more. My charges are now in school for the better part of the day and old enough that they don't need "nanny care" but they do need someone to keep their lives organized, get them to activities, etc. I am writing because I wanted to propose this to my boss in a way that proves beneficial to her. This is the note she left me today. She's a good employer. I think I could make her life easier. My hours now are from 7-6, M-F. I get the kids off to school and then I have one home at 1230 and two home at 3 & 330.  Has anyone ever made the bridge before? I am enclosing today's note because I think it shows that she would be receptive to it. I just want to make sure to politely articulate the pay difference. $16 an hour now and I would like to make at least $22.