I always dressed the kiddo normally, and then put a layer over both of us. I bought a fleece jacket one size too big. So, I'd have her in regular clothes, with babylegs down over her heels and up over her knees to keep any gaps in her pants covered, a fleece jacket on her, preferably with a hood so there was no gap at the nape of her neck, maybe a super light hat and some mittens, then the bigger fleece zipped up over both of us so just the top of her head was peeking out. I did this for both front and back carries in a Moby knockoff and a Beco (she was born in late June, we live in upstate NY so she was 6-ish to 10-ish months in the coldest weather). It was very uncomplicated; it might not have been a real pretty look, but I didn't really care.

And I think, if she's in a mid weight fleece with another mid weight fleece over her, she's going to be plenty warm in NY unless you're out for an hour in 0-degree weather. Body heat really is an amazing thing, and with all the air trapped between you and the jackets as insulation it should be fine. That way you and yoru DH would each only have to buy a good fleece in a size too big for you, nothing fancy or super expensive.
If we were going to be out for an hour playing in the snow when older DS was out, I'd just put her in her snowsuit and then put the fleece over both of us, and she was fine. And holy crap was I warm, too - but I tend to always be warm anyway and rarely wear anything heavier than a fleece all winter.