We have very similar lives! We are almost 2 months in with first au pair. I also work a lot from home. Preparation is key, write a detailed timetable of what you want doing when. Don't commit to too much work in the first week, let au pair shadow you doing everything, the more time you put in the first week the easier you make it. First month is hard work just giving info all the time. Find out where the language course is, make sure she's in the loop with other local au pairs on FB. Give her a tour of the town, remind them about parking tickets!!!
When you work from home, after the first week, let her get on with it, if she's doing tea, keep out the way, stay in your office, or wherever you work, let's her have time to bond with the kids, if you try and help too much they don't know who to listen to - I realised this by week 4, thought I was being helpful, in fact hindering. I guess I wouldn't like my boss sitting on my desk all day!
If they need help they will shout! It's a lot about us learning to be host moms! Be honest, if something matters to you and you want it done a certain way, say so up front, much easier for everyone. I'm already slightly terrified of this lovely one leaving in the summer!