
Exped
MegaMat Series
Car camping comfort king; warm and durable.

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I'm a sometimes side sleeper and for some reason I'm totally fine on anything more than a CCF pad. I honestly find a 1.5" SI pad to be the most comfortable for me including when I'm side sleeping.
I use a thermarest trail scout because it's what I have but the thermarest prolite is a bit lighter and the women's version is currently on sale on Backcountry.
it depends on what r-value you need, but honestly most sleeping pads that are thick and comfortable are going to be inflatable of some sort, either self inflating or otherwise. under a hundred you'll end up with a zlite or some other foam pad which is fine, but not very plush. I use an old thermarest (maybe a scout?) on a neno switchback and it's pretty comfy, serves me down to about 25°f. when my partner and I go camping, we use an exped megamat which is great. we have friends who use a Nemo roamer and they love it.
It's honestly just a 2003 regular grade thermarest judging by the ones I've seen as surplus here in Anchorage. Non ridgerest closed cell foam was the budget answer (and the only answer for a long time) and still works as great insulation in the cold for small money. Just information for your decision matrix - you gotta carry it all!
Thermarest trailscout is an excellent mattress around the price. Trusted brand and packs really nicely in my dry bag.
My kiddo spends at least 30 nights a year camping since she was born. Without knowing what kind of overnight temps your dealing with it’s hard to give specific recommendations, but if it’s anywhere where the overnight lows are below like 45f, I wouldn’t be putting them on something that isn’t camping-specific. We use an exped megamat duo for us and a thermarest trails scout short for our 3 yo. I picked one up on sale for like $30. And we got our megamat on sale as well for like $120. You could get your kid a megamat - they are the top of the line, or you could find something of that style that’s specifically for camping, but cheaper (I think REI makes one). Go with something that has foam and isn’t purely inflatable (the ones mentioned above are both) for durability. At 18m I wouldn’t do a cot just cuz they may fall out. And I wouldn’t purchase a cot that doesn’t have any insulation under it - it’ll be cold. We have an REI wonderland 4. It will fit the 3 of us and our stuff no problem, but if you plan on expanding your family, I’d get something bigger.
Thermareat Scout and REI Air Rail Plus both going on 5 years with several weeks and many weekends every year using them.

Exped
MegaMat Series
Car camping comfort king; warm and durable.

NEMO
Tensor Series
Lightweight side sleeper favorite, but polarizing on warmth and noise.

Exped
Ultra Series
Comfortable, quiet side sleeper pad; compact for backpacking.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with unique side rails; R-value and durability disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable; a bit 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