Hoimei, I think you would find that most Americans put their kids in daycares vs going to pre-school like we have here in HK. Perhaps you could look for a reputable daycare centers near where you live and ask them if they have a part-time schedule that would allow you to drop your son off and participate. I know my son's former daycare have some part time either only MWF or half day programs.
Your best bet on driving lessons is via word of mouth or if all else fails look at the chinese yellow pages to see if you can find one who can work out a deal with you.
it would be very difficult to recommend either a school or a driving instructor without know where in california you will be. california is a VERY big place!
Hoimei - i used to live around Sunnyvale, and can recommend some friends that can help you. If interested or if you want to join a playdate (free) with you son, pls PM me with your email address.