new to the dirt bike scene

I am a parent whose son (12) is interested in dirt bike riding.  My ex has a set up for him but rarely has the time (because of work) to take him out.  I would like to continue the interest in my home but I am clueless on how to get things started.  I do not have anything at all in the way of a bike or even a vehicle to pull a trailer with.  Is there a program you can put your child in that would not only give him the opportunity to ride but maybe offer a little advise for the parent if the child wants to pursue this activity further...maybe even compete?  I am in the East Bay, CA.