Hi Klia - Sounds like we're in somewhat similar situations! My husband and I are currently renting a house in Walnut Creek with our infant son, but planning to buy in the next year. We really like living here. Our neighborhood near Bancroft Elementary School is really quiet, and in walking distance to walking/biking trails, Heather Farm Park, Safeway, and a few neighborhood restaurants.
We've only lived here for a few months (were in SF for a few years, then in the Central Valley for a year), but have found lots of family-friendly activities so far. There's great shopping and food downtown, about a 10 minute drive - and most restaurants downtown are pretty stroller-friendly during the day. (Think we must have passed about 100 strollers in Broadway Plaza this afternoon!)
I second the recommendation for checking out the Berkeley Parent's Network. It's been a great resource for me!
All that said, don't think we'll buy here. We both work in SF, and despite being about a mile from the Pleasant Hill Bart, want to be a bit closer to the city. And while we've heard good things about a lot of the schools here, think we ultimately want to be in other districts. We've discovered the market to buy in parts of the Easy Bay is pretty competitive, so we'll see where we end up! :-)
Good luck with your search!