Since I am not quite familar with SF area, what I like to remind you is: driving in a hot weather with infant and elders requires extra care, say, driving only very limited amount of time a day. If you decide to go, you may want to consider to settle down with the kids at a place and get a local tour for your parents for the city tour (you & kids to skip the city tour).
To be honest with you, I feel neverous about your tour plan - for 2 weeks, everyday you have to take care so much and you won't get enough rest for next day.