I wouldn't recommend the
Milagra Summit Trail in Pacifica for a two-year-old, mine made it a quarter of the way but granted he just woke up from his nap and was still groggy. But my five-year-old daughter hiked to the top with no problem. The length is about a 1.5 mile loop and I was pleasantly surprised she made it up the set of long steep stairs leading to the summit; she just happily climbed with no complaints. She actually wanted to keep going to reach the highest peak and was disappointed and upset that she didn't get to because her brother woke from his nap in the car and it was time to head back.
My daughter loved the circle of rocks and we took a long water break when we reached this area. The views of the ocean are also spectacular.
The trail is in a residential area and there is a small parking lot but if it's full you can park in the neighborhood.
We came here on a cloudy day so the hike was manageable. I wouldn't recommend coming here on a sunny day around noon as it can get very hot and there is no shade as you climb to the top.