This Air BnB is an exceptionally good value - a little gem in historic Sintra. My family of six stayed for a week, including four children, the youngest age 3. The views from the windows are stunning. Sintra is truly the most beautiful in the morning and at night, when most tourists have gone, the castles are lit, and everything is quiet.
At Sonia's place, we really appreciated that the beds are extremely comfortable. The kitchen is smaller as you can see from the photos, but we still succeeded in making warm meals for our family of six, and the area restaurants provide a lot of choice as well. You can tell the owners put a lot of thought and time into making the place comfortable for guests. It is a great place if you have children, because there are no other tenants in the building, so you don't have to worry that your noise will bother others. There is also a small table in the hallway outside the apartment, where my husband was able to do some remote work and avoid our disturbances.
Some tips for my fellow travelers (especially those with children) going to Sintra:
There is a laundromat, though at a good distance walk (past the train station) and at a bit higher prices than we see in the US, but thankfully the laundry soap is also included in the price and the dryers are very fast. They accept only euros - no credit cards, no large bills.
There were some small convenience markets nearby, but we ordered groceries with Continente online, and they were able to deliver to us. However, doing this does require a Portuguese phone number to sign up for an account (we purchased inexpensive sim cards at the airport).
The train to Lisbon is in a walkable distance, but be aware that, if you are buying tickets or cards at this location, they only accept Multibanco cards or coins (no paper euro bills and no credit cards) for train tickets.
For travelers with young children, if you turn left out of the AirBnB and go down the steps, you will find a small playground. I believe they open the gate around 10 am, and the Parque Liberdade is very near as well, with chickens, rabbits, ducks, and peacocks.
TukTuks will not usually take children under 7, unless they have a booster and/or a three-point harness seat for the youngest children. Uber does not run up to Moorish Castle or Pena because of touristic license restrictions. We hiked to Moorish Castle. If you do this, I recommend leaving by 8-8:30 to avoid traffic on the upper road, especially if you have a stroller.
For Pena Palace, it is too far a walk with children, perhaps hire a touristic van for drop-off/pick-up or attempt the bus 434. 434 does pick up at the bottom of the steps by the AirBnB as well, next to the playground, but past 9 am this bus is very full and there will be a wait. We also discovered that they will pass you by for a return trip if you exit at the bottom of the Pena gardens, because they are already completely full (we unfortunately experienced this in a torrent of rain!) So, if you exit the castle gardens at the bottom, it may be worth it to walk back up to the entry of the castle for your return trip if you are taking the 434 bus, because that is where most riders are exiting.
Thank you Sonia and family, for a very memorable trip!