As long as they get there within that three-day window, you should be fine. This is kind of cyclical....every spring when we're getting our chicks, bad experiences get posted, and it seems like the disaster is the norm. It's really not, and more often than not, you'll get a box of healthy, yelling chicks, with perhaps one or two that didn't fare so well.
Regarding the weather - I'm in SD, and I normally get my chicks and eggs in this time of the year, or a couple weeks later, depending on when the temps start staying above freezing. My experience has been that, even in early spring, if they get here in the three-day window, they are energetic and healthy. The couple of times I've had chicks stuck in the PO system for four days were the instances I'd see higher mortality.
Just be sure to have a clean, dry brooder waiting for them. What I like to do for the first two days is to keep them in the basement in a large tote, with a small heat lamp suspended over one end. They should be able to get under the lamp when chilled, but they should also be able to get away from it when they want to....I don't want to cook the little buggers! I've never worried about adding sugar or other supplements to the water, but YMMV. After two days, they go out into the barn brooder. Any longer than that, and I start to worry that they won't develop the plumage needed for the cooler temps, and I have no desire for a flock of thinly-feathered, diapered chickens in the house...LOL! But anyway, same thing with the barn brooder - control drafts, give them easy access to heat when they want it, but also room to get away from the lamps when they're too warm.
