Water bottles and shorts

No metal bottles allowed in St Peters Basilica for sure for security reasons. Men wearing the kind of shorts you described is fine in churches or just put pants on when you decide to go

tmalave, regarding the shorts which don't cover the knees, I don't know as I would risk it at St Peter's, the Vatican museums or other Catholic institutions. While some guards and attending clergy have been known to turn a very blind eye where knees are concerned - and there are definitely photos out there to prove it - rules is rules, as they say, and other tourists have been turned away. For what I've read, it's at the whim of whomever is minding the door at any given point. Anyway, It's cheating a bit but might your men be able to wiggle their shorts down enough to cover most of the knee when passing the entrance?

Yes, "they" can be very strict. I saw tourists denied entrance at duomos in both Milan and Florence for inappropriate dress.

Here are the rules from the Vatican website:
http://www.museivaticani.va/content/museivaticani/en/visita-i-musei/consigli-utili.html

Entry to the Vatican Museums, the Sistine Chapel, St. Peter's Basilica
and the Vatican Gardens is permitted only to appropriately dressed
visitors. Low cut or sleeveless clothing, shorts, miniskirts and hats
are not allowed.

You, your daughter and the fellas can, of course, wear shorts with impunity on the days you don't have any religious institutions on your sightseeing list. :O)

Your boys could buy a light weight pareo and wrap it around their waist just before entering the basilicas.

It’s not that in the Catholic Church they are not used to seeing men wearing skirts

For the men, how about a pair of light weight pants with zip-off legs? Just put them back on when needed.

Roberto, you are a howl. :O)
Yep, Men In Skirts are fine (hmmm, sounds like a movie title?)

Regarding the heat? Keep in mind that religious clergy from all over the world come to sightsee Italy's jewels of the Roman Catholic Church, and many are wearing attire that's longer or have more pieces than most tourists want to put up with. Figure that if they can manage, in their full cassocks, monk's robes, habits - most with long sleeves - and veils, then covering the knees and shoulders is a small price for a peek at some fascinating churches, practically all of which are free!

We were just in Italy. They seemed to allow skirts/shorts that came to the knee (as opposed to covering knees), but I wouldn't risk it. I have a couple skirts I wear at the waist that could be worn at hip when necessary. My husband has the pants with the zip off legs. As far as the water bottles, there were places that would not allow the use of them but seemed to not care if they were stowed in a small purse. I am very environment conscious and also feel that the water in most places in Europe is excellent, thus the purchase of bottled water seems silly to me. I however, will not drink the tap water on the plane. I save the bottle that I acquire on the plane and elsewhere (juice, etc.) and use and refill until I lose them. I often will stick a half filled bottle of water in the freezer of a refrigerator when we have one. Maybe on some days you could get by with a plastic bottle?

We just kept refilling our plastic bottles from the fountains or at the hotel. Had two sets of bottles. One set in the fridge at the hotel for a nice cold drink when the day's touring was over and one set with us. Started out the day with chilled ( overnight) bottle from the fridge.
The one time we had to get new bottles was after attending a Papal Mass ( outdoor at St John Lateran). The area was cordoned off and and you had to got through a makeshift security gate. The guards took the caps from every bottles and made you empty it.

Zip off legs was my solution.

You're misinterpreting the dress code for men at St. Peter's. It isn't "shorts are okay if they cover the knees;" it's "No shorts at all - must be long pants." Here's the sign you will find all over:
https://www.tripadvisor.co.za/LocationPhotoDirectLink-g187791-d1225862-i42933734-Vatican-Rome_Lazio.html

The figures on the left are women, meaning women can wear long shorts, as long as they completely cover the knee. Think capris. The figures on the right are men. Men must wear long pants. And no bare shoulders for anyone, regardless of gender.

It's true that sometimes the guards will not enforce the rules, but it's also true that some of the guards are what Italians call "pignoli" which means someone in a position of authority who gets malicious enjoyment out of making others jump through bureaucratic hoops. Zipoff pants are perfect for this scenario.

Happy travels.

At some churches in Italy they hand out scarves for people to wrap around knees and shoulders (you give them back when you leave) and I don't see why that wouldn't be for men as well as women. But the problem is you can't count on it. Probably the zip off pants are going to be your best bet. My husband actually wears long pants (very light weight, but long) and we have been spending most of every July in southern Europe for years. He claims it doesn't make him any hotter than wearing shorts.

As for the bottles - I bring a good quality but still disposable plastic bottle with me and re fill it. If it gets too grungy to wash out in the hotel sink, or I loose it, no big deal I get another one. But I certainly don't buy bottled water on a regular basis, there are fountains all over Italy to refill your bottle. I do as others have suggested and put a bottle in the mini fridge freezer if there is one.

You're misinterpreting the dress code for men at St. Peter's. It isn't
"shorts are okay if they cover the knees;" it's "No shorts at all.

I think the problem here is not the rules on the websites but what people SEE when visiting Italy's religious sites. Add some pretty misleading ads from tour companies or candid tourist shots like these.....

https://www.romaexperience.com/roma-experiences-best-vatican-tours-and-why/

https://www.roadstorometours.com/our-private-tours/the-sistine-chapel-vatican-museums-st-peters-basilica-tour/

https://www.viator.com/tours/Rome/Skip-the-Line-Vatican-Museums-Small-Group-Tour-including-Sistine-Chapel-and-St-Peters-Basilica/d511-3731VATICAN_SMALL

https://www.123rf.com/photo_32165575_vatican-city-vatican-july-15-2014-tourists-visiting-one-of-the-halls-of-the-vatican-museums-in-rome-.html

...and it's no wonder there is confusion! Would I personally risk shorts of any sort, man or woman? Neither my DH or myself have done so 'cause dropping into churches on a whim is part of our program. We dress for the most discriminating of doorkeepers so there's never question of entry. I guess it comes down to the amount of risk you're willing to take?

Editing to add, as Stan mentions below, there's the respect factor too. Always a good idea to play by the house rules when a guest in someone else's house, eh? :O)

My two cents. Its about respect. It might be a tourist attraction to you, but its a place of worship to others who might be there too. Would you try to visit a mosque without taking their shoes off, or a synagogue without wearing a yarmulke? Not every church can afford to have bouncers and guards to police the things people should already know or take tape measures to your clothes. Yes I know sometimes communities just give up trying to enforce respectful behavior. Just because no one stops you doesn't mean its OK. Sorry if this is too strident - its just a pet peeve. Yes, I'm a boomer.

This is the water bottle we take to Europe and refill as you want to do https://www.amazon.com/gp/product/B00DM00P3M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I want to just mention that Michael's image of dress code was uploaded in 2012. I have noticed a number of updated church dress code signs in a number of cities over the past 3 years, so I personally wouldn't go by that one. I can't seem to find one on the Vatican website, but perhaps you have better luck. I am conservative and leave a church when services are in session.....my respectful action, I guess.....but I don't see wearing long shorts or capris by men as being disrespectful. Plenty of folks of all genders end up covering knees/legs with scarves when faced with the entry guards and signage so decide to either do the zip off pants or enough scarves to go around.

Stan said it about as well as it can be said. To us it's really not a big deal, even in the summer, to cover knees, shoulders, and remove shoes. We just try to be as respectful of their customs / rule as we would want them to be of ours.

Good point about the old photo. There's no getting around this, though, from the current Vatican website:
Here are the rules from the Vatican website:
http://www.museivaticani.va/content/museivaticani/en/visita-i-musei/consigli-utili.html

Entry to the Vatican Museums, the Sistine Chapel, St. Peter's Basilica
and the Vatican Gardens is permitted only to appropriately dressed
visitors. Low cut or sleeveless clothing, shorts, miniskirts and hats
are not allowed.

It is kind of creepy to basically ask 'what can I get away with'. In Italy churches expect men to wear pants -- they can't all afford to have someone enforcing it as the Vatican does.

We use plastic bottles which we freeze half full of water and then top off and slide a terry cloth bath mitt and then plastic bag over, so they don't get our bag wet. This gives cold water for hours on a hot day. and you can top up at the many free fountains in Rome.

I prefer wearing sleeveless shirts or dresses in Summer, but I always pack clothes for Europe that will cover my shoulders and knees. It just makes it easier to have flexibility to step into any church in Italy, etc.

I was surprised how people- male & female, waited in the long line for the Milano Duomo and then were turned away because their clothing didn’t meet the diagrams.

My husband just brings lightweight golf pants or Columbia sport lightweight pants.

People are turned away from entering churches if in shorts.