If this is your son's first offense, it is an infraction and the vaping products will be confiscated. With a second offense, your son can be ordered by a court to complete a tobacco or smoking education and cessation program.
Vaping by a minor (under age 18) is not permitted under Missouri laws but it cannot exactly be labeled a major crime. Your son's biggest issue may be that he was in school at the time his vaping was discovered.
Quite frankly, if vaping is the worst thing your 17-year-old son has done or will do, you are a fortunate parent.
Good luck.