Your son needs to hire an experienced and respected attorney in the Jacksonville area. I highly recommend A Russell Smith (904-355-5633). He is the immediate past president of the Florida Association of Criminal Defense Lawyers and one of Jacksonville's best.
Considering the Racing charge was found unconstitutional a few years back; an $18,000 bond is absurd and I suspect a good attorney would get it lowered quickly.
That level of bond is unusual for a racing charge, with no prior criminal history. There may be more to the charge than you have been told. An attorney would be helpful to not only getting the bond lowered to a point where your son could bond out, but also to fight the charge. Rememmber any plea to a racing charge could result in loss of driving privileges. With some more information about your son, and his name it would be possible to find out more information prior to the 24th. If you have further questions my office number is (904) 619-8185.