One of my favorite places to walk Caitlin is the Mission Trails Regional Park. There are lots of beautiful trails http://mtrp.org/trail_map/trail_map.asp , and if you go early in the morning, as Caitlin and I do, there are very few people there. It does get busy on weekends and holidays, however.
Today we walked around the Oak Grove Loop and then took a trail that starts near the visitor center and goes down to a lovely shady pool (Grinding Rocks, I think), where Caitlin likes to splash. It's all easy walking, and right now the mornings are cool and the wildflowers still abundant. Lots of rabbits, too.