Our au pair does 25 hours each week. 3 days she does 7.30am-9am (breakfast with 2 children, supervise teeth and face washing and getting dressed for school/nursery, then walking eldest to school. Same days, 3-7pm (pick up eldest from school, play, prepare tea and sit with dd while she eats it, listens to reading etc, then help with bedtime routine). Additionally, she does about 7.5 hours cleaning (mop/hoover floors, dusting, changing childrens' bedlinen) and ironing a week. I always say that as long as they choose a time and stick with it, I don't mind when it gets done providing that at least 1 session of ironing is done after Tuesday as I plough through the washing at the beginning of the week - so far both have chosen to do 3 mornings on the days they are otherwise working. Plus a couple of evenings babysitting when needed - we always use one session but often don't need any more.
I am there in the mornings and generally make packed lunches, sort laundry and only step in when needed whilst she is in charge. In the evenings, I tend to lead the way once I get home and au pair helps occupy youngest while I have some 1-on-1 with the eldest, or vice versa.
As an adult in the house, we ask that she cooks one evening each week and helps with clearing away/loading the dishwasher/washing up after we've eaten. The bins are emptied on a day I am out at work - we'll put them out ready the night before, but she brings them in during the day after the dustcart has gone past. Also, generally tidy up after herself - this is her home but not a hotel! That isn't part of her hours - she just does it as part of the adult 'team'.
Current au pair regularly goes above and beyond - little things like putting away a pile of laundry I've sorted but not yet rehomed, as well as huge things in a crisis, such as really stepping up when one child (and therefore I) was suddenly taken into hospital earlier this year. I do try to 'name check' and thank her specifically for things to show that I noticed and appreciate it. I pay £65 each week and don't generally give a cash bonus for going AAB, but I have given APs some extras I know she'll like - a lift home from the station at night so she doesn't have to pay for a cab, an unexpected top-up voucher for her mobile, a £10 gift card for the supermarket as I know she likes sweet treats and I usually don't have a lot in the house. A couple of times I've taken AP to the cinema to see something we both wanted to see but dh didn't, so we've had a girly evening.
I think it is easier that we have a defined routine that rarely changes - we all know what is expected.
I back up au pair if the kids are misbehaving always (and debrief with her later on what she did well or I might have approached differently). We almost always eat together as adults after the kids are in bed, so we do talk and connect every day and I think this helps with our adult relationship. We also invite her to come with us on family trips out - but it's OK if she declines.
Gosh that was long!