HunkerDown 20

When not backpacking I use a rectangular bag like the Rei hunker down. For really cold (<20) I just use two, one inside the other, along with layers and a warm hat. The rectangular shape is fine for some movement and side sleeping and it’s the same dimensions as my sleeping mat and cot. I wouldn’t want to go much bigger or the space inside is too large to effectively warm with body heat.

The REI brand ones are nice (and true to the temps they say they are good for). I have an REI three season single, and have used it to just below freezing with no problems.

Eh, depends on your use case. I'm in Alaska and I use a 20 degree rated REI bag. But I'm also not camping in colder seasons. If I were going out anytime other than between May-October, I'd have a -10 rated down bag.

If you can afford it before your trip, get a second sleeping pad with good r-value, such as another ExPed MegaMat for your husband to sleep on. Everyone is right in that the air mattress sounds like it is not going to keep any warmth under him where he will most likely be miserable. Also, it is not just the cold ground but also the ambient air temperature that will make an air mattress, with no insulation, miserable. Don't dedicate the wool blankets for insulation on top of the air mattress, keep the wool blankets to add to both of you for warmth. Get another quality, insulated, sleeping pad. I personally feel everything else you have will be good for sleeping. I'm able to stay comfy warm with a r-value 7 sleeping pad and 20f rated REI bag down to 25f in a tent. Tents typically do not hold in heat and is actually better to make sure you vent it well to help avoid condensation. Your warmth comes from your sleep system. The only other item I'd make sure you bring is a tarp that you can suspend so you have somewhere to hang-out out of any moisture you've stated is part of the forecast.

I would hope to trust Cabelas and their statement of r-value 7.1 but I didn't see anywhere how that was tested. Some companies make claims without facts to support their claim. Is this the case with Cabelas? I have no way to know but without facts stated, makes me a little suspicious. REI does have their Campwell Sleeping Pad that is rated at r-value 7.0 and is tested "according to the ASTM F3340 standard." The Campwell pad is 1/2" less thick than the listed specs on the Cabelas version you mentioned, so the Campwell is only 2 1/2" thick when inflated. Is it warm? Yes, it is exactly the sleeping pad I have used down to 25f with my 20f sleeping bag. The price point is right there when comparing to the Cabelas version and there are two sizes for the Campwell. Would I recommend it? Yes. You'll need to decide if the thickness is suitable but at least you should be able to try it out at a REI store first. I know the REI stores near me seem to have those pads in stock and have a platform to try it out on. Also, if you buy at REI and feel the product doesn't live up to their claims, you can return it.

I absolutely love my REI sleeping bag. It’s very cozy and warm. It’s held up for years and is still going strong.

I have an REI down bag that has been great for the past 10+ years.