Paula's place is beautiful. Near Mercado de Ribeira and Cais the Sodré station (which makes it convenient to reach by metro from the airport and for trips to the Belem, LX Factory, the Lisboa Beaches and Cascais). Also close to lot of restaurants and supermarkets (if you want to cook yourself).
The appartment looks a lot like a hotel, with a real janitor and grand entrance. This is nice (unless you look like a more AirBNB experience) and made the kids feel really special. On top of the building is a great rooftop terrace, which is fun with children (like we did), but probably even better with a group friends. Be aware the neigbourhood of the appartment is popular for it's bars and restaurants, which you will be hearing when lying in bed at night.
All in all a great place to stay and value for money!