Livestock can not be guaranteed with and form of shipping. It is very stressful. Ive worked at local fish stores most of my younger years and always we have DOA's and thats with overnight shipping. Yes the majority do fine with overnight shipping, but when you start adding days the DOA rate skyrockets. 2-3 days in an unstable temp, while crossing the rockies in a car and stopping for sleep, food, gas, etc. with no DOA's = not likely in my opinion. There is a reason no supplier will guarantee live arrival with anything other than overnight delivery.
I would figure out how your going to keep the temp constant. Without any big swings. Bags out of the question in my opinion, not enough water or air for 2-3 days, in summer heat and a car.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.