I home educate my own children and also used to childmind. I also looked after other home educated children.
I was always quite specific that I was only providing childcare, not education, for other people's children, as different people can have such different ideas on what constitutes education, I didn't think that was my role.
Having said that I found that the activities I did anyway with the minded children fit very well into an informal educational experience for all the children, the older ones did the same activities but just at a different level, so they would do slightly more complicated crafts, and be a bit more involved with the cooking process when baking etc as appropriate to their age. Visits out can usually work for both younger and older children. The only place you may find a problem is taking the littlies to playgroups as many don't like an older child to come along.
I certainly wouldn't look at doing workbooks or anything of that sort if I were you - if the parent wants them to do anything like that then they should provide suitable materials of the right age and interest for the child themselves, with you there simply to supervise.
I don't think you will find it a problem, more than likely the parent is not expecting you to deliver any sort of educational provision at all. It should all be discussed before you start anyway.
hope this helps