It is never too soon to think about transitions for both your son/daughter and yourselves.
I've attached the 2011 Alameda County Resource Guide for Adults with Disabilities. You may find helpful resources inside as you work to plan out what comes afterwards your child ages out.
I urge you to take the time to think about what type of situation you want to see your daughter or son in, when they leave Dublin High. Transitions can take time and it is helpful to visit places that you are interested in and to meet with other parents and providers to see what type of challenges may lie in front of you.
Remember, that you are your son/daughter's final advocate and you need to take care of yourselves to be able to advocate for them effectively.