We thought Carmen's place would be a bit out of the way, but peaceful and with a garden. We were wrong on the former. It is only a few minutes' walk from two very well-connected stations, including direct journeys to the airport, and at Frankfurter Allee (7 mins walk away) there is a huge department store.
The garden is indeed lovely, and the apartment, in the summer heat summer, is a cool oasis. I'd recommend this as an excellent base from which to explore Berlin. A bonus is that Carmen rents out bicycles, including ones with child seats.