Here is what I would suggest:
Adults Outerwear:
~~ One large down-feathered coat (you may be outside shoveling and you will apprciate this for any outside time longer than running in/out of stores etc.)
~~ Thermal gloves, hat, scarf, ear-muffs (nothing more uncomfortable than friggid air blowing in your ears)
~~ Also a less bulky but warm (warmer than a leather jacket, for instance) for every day wear.
~~ Also maybe more fashionable gloves for driving b/c your steering wheel will get cold, even if you are parked in a garage. Plus, you'll want the gloves for when you have to scrap your car windows.
~~ I have a pair of almost knee-high boots I wear on those sloshy days & to shovel. But once the snow has been cleared your normal shoes will be fine.
Your Son:
He will probably want to play in the snow, so here are the essentials
~~ Warm, warm coat - bought my kids coats where the inside lining can be worn in or comes out and doubles as a lighter jacket - these are great and add extra warmth (I get them at JCPenny).
~~ Snowpants
~~ Boots, thermal gloves, hat (I get the ones that cover the ears and cheeks too), scarf
Does your son keep the covers on himself at night? If not, then I'd put long underware under his feetie-pajamas. Usually in the winter we stay in most of the time are are comfortable in sweats (usually with a t-shirt underneith).
I'd also invest in a good down comforter for your bed and your son's as well. You will not get cold at night with one of these. They are so, so comfy.
For your car - the ice that sticks to your windshield will tear your wipers up so I always have an extra pair b/c I hate a smeary windshield. Get the de-icing windshield fluid and don't forget a brush scrapper for the windows to keep in your trunk.
All the best! Be glad you weren't here last year when we got 18" dumped on us in 24 hrs.
Also - I get all the clothes at stores like JCPenny & Kohls and the hats etc can be found at Wal-Mart or Target or something.