This is the right decision so that you will have consistent uninterrupted care with less germ exposure.
But also it's pretty great generally. You can ask her to take on some minor household tasks too like dishes, laundry and general tidying. It is so nice at the end of the work day to have those things done and just focus on the kids. Also, not only no commute, but you don't have to get the kids dressed for the day and out the door. Basically all of your time with them during the week can be real quality time.
Agree with PPs regarding having a private space to work and giving nanny room to do her job. Try not to emerge except for agreed to times like lunch. If you hear the kids yelling or upset, don't intervene unless you think someone's actually in danger. Nanny needs to learn your kids - and frankly, you are paying well for this time and you should use it to work (or treat yourself to some self-care if you have downtime). I text with the nanny when we need to communicate during the day after "dropoff" or before "pickup."
The day the nanny started was the day I felt like I could really get through COVID for the long haul. We're also in a small home, but the key has been giving the nanny and kids free run of the house except for work spaces.