We enjoyed our stay at Ricardo and Katy's place. There was definitely enough space for the four of us. The apartment is very atmospheric and the location is great. Iola and Maria (who help Ricardo manage the place) are extremely good communicators and provided some great recommendations and insights.
Keep in mind that the bedrooms are not too sunny (with the ubiquitous slopes in Lisbon they are effectively in the basement with smaller windows by the ceiling) -- but it also makes them very quiet. It didn't bother us very much.
On the opportunity side, I'd recommend Ricardo to install Wi-Fi extenders throughout this spacious apartment because the signal is not great outside the living room.