The Montara Mountain Trail in Pacifica was one of my favourites this year. The trail is fairly steep, but it has breathtaking views. The parking lot and picnic area set the tone - a peaceful, lovely trail. We didn't make it all the way to the top of the mountain - when you hike up, you reach a spot (quite a way up) where the vegetation ends. The straight path ahead goes to the top of the mountain, while the split heads off left and down the mountain. We took this split (I no longer remember the name) and came down the mountain - coming down was a lot of fun too, with a narrow trail and lots of scrambling.
If I remember correctly, we turned around at this point:
The 5 y.o. was keen to reach the top of the mountain, so we might return here to complete the hike.