
Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

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I use a king size air mattress from Decathlon. It's pretty comfy. But it has no insulation. So when I camp in colder areas I bring along my Therm-a-rest Trail Lite and put it on top. It's all a bit excessive and bulky, but it's comfortable and doable with the rest of my pack. With that said, I'm looking for a better double width, insulated sleeping pad or air mattress that would pack down smaller.
Do the kids really need such a sleeping pad? Why not just some closed cell foam mats (e.g. Nemo Switchback or cheap clone) for them? I also wouldn’t be too sure that the Megamat is a cure-all. The girlfriend and I once had to sleep on some big inflatable guestbed mat thing which was horrible (especially with two people). To this day the most comfortable mat I know for me is the Therm A Rest Trail Lite since it has a flat surface (no ridges), is firm, doesn’t bounce, has a nice textured surface and makes no noises. Even though it’s “only” 3.8cm in thickness.
My first winter camping trip is one I’ll never forget, my back was killing me after trying to sleep on a foam pad. The next trip, I brought a Therm-a-Rest Self-Inflating Pad and it literally changed everything. Suddenly, I was sleeping warm and supported, ready for morning hikes. I’d recommend [air mattresses](https://www.reddit.com/r/KeepThisInMind/comments/1ltzxk1/recommend_the_air_mattress_best_for_camping/) for camping to anyone, from lightweight backpacking pads to thick car-camping mats, especially for winter trips.
I've used a self-inflating Thermarest under a Big Agnes pad...half inflated
I know that I have two just like this, but I’ve always inflated them by mouth. Maybe I’ve doing it wrong for 25+ years, but either way these are great thermal insulation for camping.
Before you commit to cutting a pad you may want to consider the pad thickness, how the resulting drop in height might affect your sleeping position and how you could compensate for it in practice. The Nemo Tensor All-Season specs list it at \~9cm, which you'll of course sink into some depending on inflation level, but it may be high-enough where you would need something more besides your empty backpack to rise the legs to similar level. The Therm-A-Rest self-inflating one would have probably had 3.8cm height according to the specs. Guessing based on the specs of the currently available self-inflating ones.

Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

Exped
Ultra Series
Lightweight side-sleeper comfort, but a bit pricey and bulky.

NEMO
Tensor Series
Ultralight side-sleeper comfort, but slippery and prone to leaks.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with side rails, but heavy and warmth claims disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable, good service, but heavy and bulky for backpacking.

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Therm-a-Rest - NeoAir Xtherm Series