Naturally, make sure your son attends the hearings / appearances. You may be able to meet with the city attorney before doing any court appearance. If so, the city attorney may already have some level of discretion to adjust the fine and any plea agreement. Or it may go straight to a court appearance before a judge.

Just don't allow yourself (or you son) to come across as non-contrite or combative. Acting like a jerk or complaining will get you no where (or make things worse). Have your son be honest and express his desire to fix things and make restitution in whatever way the attorney / court will allow. Respectfully ask what options are available to lessen the fine / penalties, if any. They may simply cut the fine down or allow for community service or taking a class, etc.

This is his first ticket I assume. If so, that may work in your / his favor as well.