@otienosmall
The househelp is not legally obligated to disclose her HIV status to her employer. If she had done so during the recruitment process, you probably would not have given her the job. She has a right to speak out or not speak out about it.
The fact that she is on ARVs means that either her CD4 count is quite low, as low as less than 350, or that she was/is at a WHO HIV stage that necessitated the ARVs. This means her immunity is low and her body may not have the ability to fight illnesses as well as it should.
Considering that the househelp takes care of the children, and children naturally have not developed their immune systems fully, it could predispose the children to illnesses. Think of skin infections such as herpes zoster and candidiasis, diarrhoeal diseases such as Cryptosporidium, and other serious diseases such as Tuberculosis.
Children cannot decide between wrong and right. And adults seemingly judge situations better than they do. We as parents have a role to protect our children from any harm that may befall them.
I have often heard boys and men declare that their first sexual contacts were with househelps. Your 9 year old boy might indulge and get infected. It is likened to having bare electrical wires at a socket outlet in the house, and hoping and hoping, that your small son or daughter does not touch them. Fix it. Now.
I am biased towards children care. I have no objections towards living with a HIV positive person in the house, as long as the interactions are between adults, with mature mindsets and devoid of stigma. But you should strongly consider whether it is wise to have your child care provider being HIV positive.
Else, make sure that she is solidly counselled and understands that she has an illness that portends a health risk to the children. That she comprehends compliance to her medication, adherence to her ARV clinics, prompt treatment for opportunistic infections, hygiene in contact with the children, proper disposal of body and blood products, proper nutrition for herself and open communication and full disclosure to the parents in case any of her health conditions change. Regardless, HIV positive mothers carry their babies to term, deliver safely, and bring up their children to be healthy and HIV negative. The househelp can accomplish this too.
Set out to correct the world's wrongs and you will most certainly wind up adding to them.