A very challenging situation. As a 15 y/o, there will be no permanent record, but in all likelihood you cannot control or dismiss the charges, since they are brought by the state of Maryland. Your involvement will be critical, and it will in all likelihood turn out fine ~
There are so many other questions which come up:
Is this the oldest child, or one of a few? How is he doing in school? otherwise? Is there indication that he understands how wrong this was, and how credit cards work? Does he have any type of allowance, or ability to earn money for certain chores, or in the neighborhood? What does he understand of money, and how it all works? At age 15, he would love to emulate you, and be able to have some purchasing power . . . what did he try to use it for?
As you can see, this is so much more a family matter, and counseling matter or discussion matter, rather than a legal type of matter, beyond the fact that it would have been illegal for him to use the card.
So, stay involved. You may want to consult with an attorney to see if this can be carefully steered to a softer type of early closing. Even without an attorney, it will turn out ok as long as you (parents and son) remain ok and do not over react to what is unsettling, but not totally unexpected behavior of a 15 year old.
I would fear your son will likely learn even worse tricks in the juvenile justice system which has an admirable record of turning out young recidivist criminals. As a parent, I would find a more suitable way to correct behavior such as counseling or requiring your son volunteer some time at a non profit charity. This scenario really seems like a waste of tax payers money since even community service requires government paid supervision.
This is not legal advice but a general comment on society.