This is exactly the subject I was hoping to find!
We live in the arid mountains of northern Ca and have been having temps in the 90's to low 100's and it is hard to keep our place livable in the afternoons/evenings. We just moved into a 30 ft yurt and re insulated our roof with the reflective bubble stuff, 2 layers and put R13 on the walls and covered it with wood siding and put in a ceiling fan and I can say that now the yurt definitely retains the heat! Which I'm sure we will be grateful for come winter but it seems like an oven in thereafter about 2 pm and stays hotter in there then outside temps until into the night. We don't have solid windows so the option of buttoning up in the a.m. is mute. I like the idea of heavy dark curtains though, good for both weather extremes. We have a dome that vents out the heat which we will cover come winter.
I just gave birth to our 2nd daughter 1 week ago and have a 2 year old and we pretty much vacate the yurt to the shade in the afternoons and that can be hard to not have the comforts of home (when you're nursing, pumping, supplementing for nb and mommying a toddler!) I have been concerned about our little one getting too hot and keeping cool clothes on her and wetting her hair and keeping her well hydrated. And she seems to be doing well.
I have to wonder if the temps were this hot 100 years ago and beyond.. Because obviously native and pioneering babes endured the harsh weather conditions with out many comforts. My guess is they do what we do and live by the creeks and rivers and on those hot days set up day camps in at least 6 inches of water!
I also rec setting up a simple outdoor kitchen; propane burner and BBQ. Many meals can be made like this. Don't use your appliances that can heat up your house, who wants cakes and casseroles when it's 100 degrees anyway! Go to the garden for fresh salads. We have a basic solar oven and when I'm on it, I throw quinoa, beans, bells, onions, greens, spices etc.. in the night before to let them soak and put in the sun oven in the morning and we have a delicious nutritious meal in the evening. I have also made chili in one and corn bread in another, or soups or anything you would crock pot. That way you don't have to cook or do dishes at the heat of the day.
Lets here some more tips on keeping kids cool and entertained in the heat..