Great place to stay! The hosts are very friendly and responsive. We had no issues to stay with our kid (<2y). The garden in big, green and beautiful, the old tree is amazing.
If you're using baby stroller a lot, be prepared that you'll not be able to use it on the road between Sintra center and this location. The road is very busy, narrow and walking areas are about 40-50cm wide. Actually all the roads are about the same in Sintra.