You had trained for a marathon but ran half that distance. How hard did you go at it? How much time do you have to your Vermont alternative? Do you just want to complete the marathon or do you have a goal time?
If you are feeling not too beat up, and are planning to run at the end of May, give yourself ten days or so of easy running to recover, get a long-ish run in three weeks before the marathon and then start to enjoy your second taper. The next few days would almost be a reverse taper - start building up again but not too hard. You should already have the endurance necessary, and if completion is the goal, just be careful not to do anything too extreme.