I don't think you could find a better apartment to stay in in Lisbon if you are travelling with a small child/children. We were with our 16mo and it was perfect. The apartment was spacious, clean, had a well equipped kitchen (including a washer/drier) and had a highchair and travel cot. The beds were comfy and there was a lounge, including a TV with netflix for once baby was asleep. We did have a few issues with the hot water but these were manageable/fixed quickly. There was a lift, so no stairs to navigate with a pushchair/suitcases.
It is right on lots of bus/tram routes so getting round was really easy and we were able to walk to lots of places too. It's within a 5 minute walk of a supermarket, park, bakery and lots of tasty restaurants. I would definitely recommend this apartment -one of the best Airbnbs we've stayed in.