can i attend the magistrate court with my 17 year old son

It probably depends on where he is. If he's already bonded out of jail and the "magistrate court" is simply his first appearance in the County court, you can probably be there (some courts will empty a courtroom during busy dockets so that there is room for the defendants). If he's in a big County like Harris County, magistration is usually done by video teleconference with inmates who haven't been released yet.  Fear not, though. Magistration suggests he is at the beginning of the process. The best thing to do is to hire him as good of an attorney as you can afford. Speeding is a legit reason to be pulled over. But, that doesn't automatically give an officer the right to search a person's car. If the search and seizure are legit, there are resolutions available in most places for those who have no priors, that will allow him to avoid a conviction.