Oakland Boo at the Zoo also on Saturday 10/27

Oakland, CA...October 27 & 28 - Bring your little pirates, princesses, and pumpkins to Oakland Zoo's Boo at the Zoo. This year's festivities include a spooky scavenger hunt, a cute costume parade, free ride ticket for kids in costumes, and Halloween treat bags that feature palm oil free candy. Get your ghostly gear ready, grab the kids, and see how the Oakland Zoo celebrates Halloween.

Boo at the Zoo is from 10:00am - 3:00pm, with the costume parade at 11:00am & 1:00pm. Admission prices are $9.75 for children and $13.75 adults. Parking is $7.00 per car. Boo at the Zoo festivities are included with general admission.

Free Admission to Chabot Space & Science Center Saturday 10/27

Chabot is hosting a free day on Saturday, 10/27 from 10am - 10pm with free shuttle rides from Fruitvale BART to Chabot. The event is called Flash Mob Science

From their website:
Join us for free admission to Flash Mob Science at Chabot. In addition to Chabot's interactive exhibits, hands-on demonstrations and Planetarium shows, there will be "flash mob science." Flash Mob Science is guided hands-on experiments dealing with energy, light, sound, gravity forces and motion and is meant to instill children of all ages with the power of possibility.