They will continue to sprout long, thin bleached stems if kept in the dark. I would seriously consider putting black plastic or spun bond row cover over the spot in the garden where you want to plant them to help warm up the soil faster, and leave it there until you actually are ready to plant. Then put the potatoes somewhere with bright light and as cool as possible temperatures indoors, but not wait a full month, more like 2-3 weeks. I put mine in egg cartons since otherwise sometimes they roll and the sprouts break off. After you have planted you can replace spun bond row cover and it will keep things a few degrees warmer, but don't put plastic over them since you can quickly cook the new sprouts.

That said, you could probably plant the potatoes now and they would be OK as long as they are deep enough to not freeze. Every year I have some potatoes that I miss when harvesting, and they sprout in the spring. Also, in the future, you might want to send a message with your order that your zone 7 has delayed warming due to its location on Cape Cod (you are nothing like zone 7 farther south) and you would like your potatoes in mid to late March.

Okay great thanks for the info, I'll do that for sure. I've read conflicting opinions as to whether now is a good time to plant them, but I'm getting some row cover in a few day and might just put them in when I get it. Next week is supposed to be warm so perhaps they will be okay... Thanks again.

I'd let the soil warm a bit first - since it will be warm next week, it might be best to give it a few days to start warming with the row cover before actually planting

I've shade over half my garden until about mid April, so I get out there in the last week of March with a pick and turn over the frozen soil and it thaws out in a few hours. I can get away with this because half of a small plot is fairly easy. I must do this because I'll have the same problem with onions. I lost 2/3rds of the onion plants I ordered in 2015 (the soil frozen so hard and deep that even a pick wouldn't sink into it until April 10). I might consider turning over the potato patch if I were you.