selling alcohol to a minor

I recently received a ticket for selling alcohol to a minor.  When I checked the purchasers id I checked the year of birth against the one posted on our monitor for tobacco rather than for alcohol. When the local LEO came in to confront me I stated the date of birth to her only to realize when repeating it that I checked against the wrong year.  I was ticketed for selling beer to a minor and cooperated fully.  I spoke with a prosecutor about potential options since I am planning on applying for a position with the US Marshals when I finish my graduate MBA program in approx 2 years.  She then spoke with the officer and mentioned that I could go through a pre trial intervention program which will likely cost in excess of 1000 dollars. The fine would be much smaller if I plead guilty though will go on my driving record.  Apparently this offense is an infarction against your drivers license instead of criminal record in SC.  I work full time and barely make enough to pay tuition (8.30/hr) so a cost effective option is necessary for me.  I was curious as to whether or not any person could perhaps give me some advice as to how to finding a solution to this matter.  I made an honest mistake and haven't even received a speeding ticket in over 10 years.  I was curious as to one potential option.  Since this is a ticket that goes on my driving record, would it be possible to plead careless operation, which is from what I understand a catch all that allows no points taken from a license albeit at a slightly higher fine?  I really don't think a selling beer to a minor would look good when applying to the US Marshals.  Further the 1000 PTI cost would account for over 10% of my yearly take home income, which I'm sure any reasonable person would consider VERY financially significant.  Much thanks for any help or insight into the matter.