part-time Nanny pay?

I'm going to try my best to explain the situation so you have some background but I'll need to summarize or it'll be a novel.
     My 3 year old has developmental delays and has been in Early Intervention since 13 months. We enrolled him in a daycare for social aspects in 2015 where his therapists would go to provide his services. (Had to be a center approved for his therapists to go.) Fast forward to current: we have him seeing a bunch of specialists and also just started him in a PREP program for more individual services at his Elementary school along with the Early Intervention and now his therapists provide the services at his new school. His daycare got really nasty with me at a meeting that his therapists were no longer available to their facility because of his new school... I even asked his speech therapist to attend the meeting with me and we are disgusted by the things that were said to us. I also am returning to work next week from maternity leave so I have a newborn and removed my 3 year old immediately from the daycare. I'm hiring a part-time Nanny/sitter to babysit in my home as I work from home some days. I will provide everything and the woman we are hiring has never nannied before but she is a mom so I'm perfectly okay with her bringing her two sons (my husband and I really like them and feel good about this) she will have my 3 year old from 9:00am-12:30pm Mon,Tues,Wed,Fri and 9:00am-2:00pm on Thursdays. She will have my newborn 9:00am-2:00pm Mon-Fri. I will be working from home a majority of the time so I will be here if she needs me (I work for insurance and make phone calls so I can't have the kids in the room while I do that or I could lose my job.) we are paying her $150 a week to start and we can increase if it really works out. She will be bringing her 2.5 year old (which I'm excited for socially for my sons) and her newborn as well. Do you feel the pay is fair? She has already put her notice in at her current job and I know she's excited to have her boys with her now too. (We live in Pennsylvania and I'm paying her under the table) 
Opinions please :)