Sandra and Armin's place was the perfect place for our family of 5 (kids 1,5 and 8) to explore Vienna from. Sandra was very attentive and conscientious about informing us of any new rules (pertaining to COVID-19) and quick to respond to any questions we had. We visited in July and the weather was nice and warm. The place is not even a block off of the pedestrian mall where the subway is and all sorts of stores are, also practical stuff like grocery shopping. So whether we wanted to sit down for dinner, get some take out, some ice cream, or cook back at the appartment, everything was possible. The subway is real easy to use, but we also had a car. We wound up parking in the parking garage on the corner to unload our stuff on the first day, then I took the car to the Park and Ride and left it there for the week (I think it was like 22€ for 6 days) (for me the 2nd to last stop Kendlerstrasse was closer to the P+R than the terminal stop Ottakring just fyi)
The Haus des meeres is an aquarium/jungle built into and huge bunker which is about 2-3 blocks away. We went early one day and there wasn't any line, but we also went back to the area because there's a nice playground right there too.
We had a wonderful time and were happy to get such a well located place.