If you are not already riding as a group, you should try to link up with some other riders along the way. Then you will have company while eating at the restaurant, and also for the BART ride back to Orinda.
At this time of year experts recommend that you drink one full bottle of fluid (with electrolytes) every hour on a long difficult ride like this. Plus, if you are getting hot, it will help if you replace your warm fluid with ice-cold fluid at each reststop -- you are less likely to overheat if drinking cooler fluids than hot ones.
If you are getting any of the signs of overheating, you should immediately stop to rest -- and flag down a SAG: they all are carrying ice-water that you can pour over your head and jersey for a much needed cool-down. Some of the signs to look for are light-headedness or disorientation, a sudden feeling of getting much hotter (flushed), and/or a general weakness overall (not just your leg muscles).
At each reststop you should eat a good amount of energy food and a small amount of protein, without overeating. You need to keep fueled for the long effort, but not get your stomach loaded up so it expends a lot of your body's resources digesting a big meal.