We stayed here as a group of 5 including two young children. It is a fabulous apartment and really huge. It was very clean and well presented and really well equipped.
The location is great with lots of nice cafes, restaurants and shops nearby, and a supermarket just around the corner. We liked that it wasn't too busy or touristy compared to other parts of the city. There is also a park with a playground and cafe (Jardim Estrela) 10 minutes walk up the hill. It was about 15 mins walk to Cais de Sodre train station and the Time Out Food market, and the departure point for boat trips.
The iconic no.28 tram runs right past the front door which was great for travelling to the castle, but bear in mind it is quite noisy (although the bedrooms are at the back of the apartment so it didn't disturb our sleep).
For other families staying here, we'd recommend a day at the beach at Cascais (30 mins by train), the Oceanario Aquarium, the Barco Evora boat trip (45 mins, children are free), the Monsanto playground ('Alvito' - free and easy to get to by bus), and fab ice creams at Nannarellas and New Moment.
Maria was great at communicating and we were met at the apartment and showed around and made to feel very welcome. All in all we had a great holiday and would recommend this apartment. Thank you!