WL,
I agree, that if you want to plant them this year, do it now. You're taking a big risk doing it in the fall. They aren't like typical trees, where it's recommended to plant in the fall. In MY experience, for zone 7, late May/early June is the best time to plant in ground because frost season is over and you have several months for those young trees to adapt to the ground soil. I've actually had better luck planting 1 year old trees over 4 year old trees. Perhaps it's because they can adapt easier with a smaller root ball. I've even planted 3 month old cuttings/trees in the ground with great success. But again, they were planted early in the season. Another advantage to planting early is, even after a harsh winter, they have a better chance of surviving due to a strong well-adapted root system in the ground. You'll get die-back from a bad winter, but they always come up from the base. Again, all this is based on my own experience.