Send an email to: mashleywedding@googlegroups.com
Yes, there is a parking lot at the venue. Keep in mind that it is public parking so it's first come first serve. And don't leave valuables in plain sight in the car!
Oakland has a temperate climate, generally not too cold or too hot. In the month of May, average temperatures are between 65-75 degrees during the day and between 50-55 degrees at night (Source: https://weatherspark.com/m/541/5/Average-Weather-in-May-in-Oakland-California-United-States). So don't forget to wear layers, and be sure to have a jacket and/or scarf on hand!
This article has a great overview on what areas of Oakland you should visit and what areas you may want to avoid: https://travellersworldwide.com/is-oakland-safe/