IMO, whenever you have any criminal history (arrest for domestic violence with dropped charges included), i believe it is in the person's best interest to consult an attorney. Although dismissed charges are unlikely to be an issue, an attorney will advise you of the documentation that should be in your hand in case there are any questions. It is worth the cost of the consultation for the peace of mind knowing that you have prepared.

On a more personal note, I hope you and your fiance have taken advantage of family counseling to minimize the chance of this occurring again.