We had a nice stay in Sintra with Villa Lunae with our two kids. The apartment is ideally located, literally 5 steps away from the train station, and with parking space nearby (which is not obvious in Sintra). The apartment was nicely decorated, well equipped and clean, with a huge terrace for a morning coffee in the sun. The terrace is the only place where one can hear the trains, the rest of the apartment is very well isolated.
The only improvement I would suggest is the reactivity of the host, who took over 24 hrs to respond to one of my messages.
Otherwise a great stay, highly recommend!