I have read several discussions about what women should wear but not a lot about what the men should wear. Would my husband and father in law look completely out of place in shorts or would pants/jeans be better?
You asked, "Would my husband and father in law look completely out of place in shorts..."
"Completely" is a strong word. Let's just say 90% out of place.
Shorts are occasionally worn by men in northern Italy, but only when it's extremely hot. Shorts are very rare on non-tourists in the south.
Wearing shorts will probably define you instantly as a tourist. The locals may frown or roll their eyes, but they won't hit you or anything. :-)
Just remember that you can't tour a church in shorts.
In towns and cities, pants are better.
Shorts are OK for the beach or for hiking.
I would only plan to wear shorts at the beach, pool or while hiking/playing sports. Jeans are bulky, heavy and hard to wash/dry.
Lightweight pants are the better option.
I did a visual packing list. It's basically what goes in my carry-on for anything up to a month on the road. I couldn't get websites for exactly what I have but it gives you a good idea what to pack and where to get it.
Check it out at this address.
I've been looking online for photos of Italian street scenes, searching for the "everyday look" of the typical Italian man, age about 50. I haven't had any luck. Mostly all I find are photos of teenagers or tourists.
But I picture mostly dark, subdued clothing without a lot of busy patterns...the opposite of the stereotypical tourist to Hawaii.
I lean toward long sleeve shirts in all weather. Contrary to what most will think, if you're in direct sunlight you are cooler in long sleeves (the desert dwellers have always known this) because the sun heats up your clothes rather than your skin. With the layer of air between the shirt and the skin, you're protected from the heat. Same goes for shorts!
When you're in the shade, roll the sleeves up to let the breeze evaporate perspiration. But when you return to the sun, roll the sleeves down.
I learned this as a child from my grandfather, a carpenter who worked all day in the Arkansas sun before the days of air conditioning.
Assuming it is not beastly hot when you are going, have them both take a lightweight blazer with them. My Navy blazer was handy to dress up whatever I was wearing, and having the extra pockets was helpful for water bottles, guidebooks, maps, etc. Since it is bulky I just wore it on the flight over.
If you are comfortable wearing shorts at home you will be comfortable wearing them in Italy. I have been going to Italy since the late 60's when I was playing basketball there after a stint in the service. I go every September and wear shorts if the weather permits with never a comment or rolling of anyones eyes.
Light pants...khaki or linen, work fine. No jeans, especially in the summer. Shorts are fine in the Cinque Terre for swiming, hiking, etc. Personally, I was cooler with my loose fitting long pants. As stated earlier, if you plan to go to the old churches there, bare legs for men or shoulders for women are a no no.