My experience with planting tomato's slightly earlier than when ideal, has not been good.
In my best case scenario, they simply stopped growing, and remained basically stagnant until the weather had warmed up significantly. They were actually smaller than if I had just left them to plant outdoors later when it had warmed up.
In the worst case scenario, they developed blight, and died.
At the very least, I would plant them under some sort of makeshift cover, till all chance of frost is well past. It will protect them from the dew as well.
It is frustrating when any veggie seedlings start getting leggy like that. I think that it has to do with a combination of the lighting, and perhaps lack of air movement around them. A low speed fan may help toughen them up a bit and become more thick stalked, whereas the ideal light spectrum and brightness, can prevent them seeking more light. Natural daylight seems ideal..if it's available..lol