So she is a nanny and housekeeper?
Enjoys children, patient, smiles, and trustworthy.
Common sense, including common sense about safety issues.
Safe driving record if she will be driving them anywhere, CPR certified.
References. Background check. Credit check.
Bilingual English/Spanish would be a plus.
Will she be living in? Which reminds me, I would only hire a woman, and I would consider the possibility of my husband falling for her even though I trust him.
The activities would be pretty much everything. She could take them to the park, shopping, to and from school, out for a treat like ice cream or similar, teach them to cook, bake cookies. If you are only out of the house a couple hours at a time it is more like she is just babysitting now and then, and no great thing has to be done, they can play and she is mostly there for an emergency situation God forbid. If you are around most of the time she is just another adult in the house the children have available to them. It would matter what her competency level was, her other duties at the house, and how much you and your husband are around and how many hours she is with the kids.
If you are actually home most of the time, I would have her focus more and housework, and I would play and care for my children for the most part. If she is helping you with an infant, I would try to work out a routine to help with feedings, if you are not breastfeeding, and changing the baby. Still, primarily I would want her to help with laundry, cooking, and cleaning, but since you say nanny, I assume her primary responsibility is actually minding your children.