I would ask her what she really wants. I think everyones circumstances are probably different. She might want you to entertain the children so she can have some "me" time. Thats what I would have liked when mine were small as I dont have any family to help out in that way.
It will probably change every week. I have a volunteer for 2 hours a week and my dt's are nearly 9 months, with 1 at school too. My volunteer has looked after the dt's whilst I napped/did housework/did the school run, made up bottles, taken dt's for a walk, come to medical appts with me etc etc.
Don't go with any preconceptions. I had a Homestart volunteer who seemed to believe that what she thought I needed took precedence over what I actually needed. I was BFing so couldn't actually leave the boys with her - so I took the time to catch up with emails/ do online grocery shop etc.
In the end I stopped her coming as she believed I should be trying to "get out more" and use her to enable me to do so - i.e go to twins club or out for coffee. I mean, why on earth would I want to go "for coffee and a chat" with a stranger - I've got friends I can do that with.
She also "wasn't allowed" to change nappies or give any other "physical care" - because that put her (yes, her) at risk (of what, I'm not sure.)
Basically she and her manager were a waste of space and I was very disappointed.
My homestart lady spent the morning with me and the boys today. We went to Asda and for coffee. It was great to be able to sit in starbucks without people tutting and huffing about the double buggy being in the way (we took the macs). Next week if it is fine I will mop all the floors whilst she keeps the horrors off them to dry. Whooppee . Doesnt sound much but I cant do that on my own without wishing I hadn't bothered.