Your tomatoes will be in the pots for about 6-8 weeks. We never plant before June 1st. The weather in south Dartmouth is too likely to be cool and wet until June. Tomatoes languish in cool wet soil. Planting them before June risks a very bad start for no apparent gain. Tomatoes planted the first week of June do as well or better than those planted earlier. They ripen at the same time! There is no perceived benefit to justify the risk of exposing them to bad weather conditions. There is an emotional urgency to plant early, I know. I have succumbed many times. But try to put a lid on it, for your plants' sake. Plants that get off to strong start seem to do much better throughout the season. Plants that get off to a weak start never seem to flourish.