to leave usa and come back-waiver/pardon

Ok the problem i need help with is this.. A canadian citizen came to the usa without a visa-crossed border with i.d only-so no record. 1yr later was tricked ..cashed 3 fake checkes and was charged with 3 consecutive charges of forgery of a commercial instrument..took time served of 6mo(no contest) instead ofsitting in jail for 2 yrs waiting for trial. now 5 yrs is almost passes and the person has a child(3yrs) in the usa with a usa fiance (cant marry yet-still married in canada-but got the divorce in usa already just not in canada -can't leave usa yet) they want to be able to live in usa eventually-legally or be able to cross (daughter/fiance sake) how would they do that?? they are in the usa now.. whats the best way to go?