Picnicking/visiting vineyards questions

I brought a corkscrew and reusable utensils to France and Italy. Locale is everything re whether you are being gauche - see if the locals where you are have hauled out the sandwiches (probably they haven't) and follow suit. Left the corkscrew in my hotel room when going to museums, because indeed I thought it could be confiscated, and it was a good one so wanted to keep it. The utensils came in really handy for room picnics, and they stood up fine to the cheese, butter, bread etc. (mine were from Old Navy but yours look sturdy too.) I was on a RS bus tour so can't speak to the DWI situation.

One reason I always check luggage on aircraft is so that I can bring a pocket knife, plus a small cheese knife and a corkscrew (with foil cutter, not TSA approved). Unfortunately, I often have to leave them in my hotel when going out to sites in the city. In Paris I tend to eat in cafés and restaurants instead of picnicking, but I do sometimes bring food back to my hotel room. Unless you smuggle them, knives and corkscrews will likely be confiscated when entering museums and monuments. And some places don't have a methodology for getting them back to you. But in the more rural areas I typically visit, I bring those and a small cutting board as part of my picnic assembly every day when heading out. YMMV

Be realistic. Are you really going to be strolling Paris between your sights and grab a bottle of wine and sit in a park and drink it? A whole or even part of a bottle? Then carry around the rest the next day in case you feel you need a picnic? That is what cafes or wine bars are for. Carry around that bottle even after you the first picnic on the same day?
It sounds French, and romantic.but it is really lugging around a bottle, cheeses, bread, and utensils all day.
If you do not usually drink too much, there are about 5 glasses of wine in a bottle, so you have perhaps three days to get it all down. Same wine too.
The allure of such a dream will quickly become a burden.

I like to picnic in Paris but not on the fly -- although sometimes we pick up sandwiches to eat in a park. You do go through security at museums and a knife will be confiscated but in our experience, they keep it and return it to you when you leave -- we have done this at Louis Vuitton, and at at least one other museum as my husband routinely carries a small pocket knife and sometimes forgets to leave it in the apartment when we head out.

Lots of people picnic in parks on the Seine; there are parks at the tips of the islands that are quite lovely. Tuilleries and Luxembourg gardens and really any big park will have picnickers. People drink wine at picnics all the time. One is discreet. The no wine in public thing is what empowers the police to roust the drunks in Champs du Mars, but people are rarely bothered with a picnic in a park as they enjoy a little cheese and fruit for lunch.

You can't drink and drive. Someone has to be the designated driver and perhaps enjoy a glass or two back at the hotel or apartment. We often try to arrange dining in walking distance of where we are staying or if we have an apartment in the countryside, we cook in.