Why would you want to exclude your family from this??? Their baby girl is getting married, they would want to be their and it would be wrong for you not to tell them after all they are the ones who gave you life....
It is not wrong to get married at the court house in fact that is how my husband and i got married, we married at 18 and 20 and we had another wedding a year later, but you should really tell your family..
Are you going to have any witnesses? you will need to! We had to have at least to witnesses their, and they were my family