Can I get by In Paris and Rome by carrying very little cash and using the credit card for every little souvenir, tour and food purchase? Or should I prefer paying in cash for both Paris and Rome? How widely accepted/common are payments by card?
In France you can almost always pay with a credit card but for small amounts (say up to €10,) cash is often preferred. In Paris cards are a little more often accepted than in small towns off the tourist track.
I have not been in Italy, so not in Rome, but I have heard the same for there.
Get some cash and use your card for the bigger payments. If you are low on cash, check with the restaurant before you start your dinner. Most of the time there will be an ATM near, but you might prefer an other restaurant.
And not all credit cards are as easily accepted as others. Visa and Mastercard work almost everywhere, American Express less and other cards are rare or unheard of.
Best check with your bank that your usual ATM card is ready for use abroad and tell them that you will use it in Europe, and when. Also check with you credit card company. If you have the choice think about replacing your credit card with a chip and pin, as those are the standard in Europe.
Ask about the cost for each use, both for the credit card and the ATM card.
Get about €200 out of the ATM, or from a bank at home, and get some more when you are seeing the end of it. That way you will not be left with a lot of euros. Nor will pick pockets have a feast of your money.
You should expect pick pocket at any touristy place in the world, as well as any busy place. Tourists are an easy target but all people with some money or valuables can find them gone at unexpected times.
I just got back from a 2 week vacation in Venice, Rome, Amalfi Coast, and Paris on Monday.
First, note that Espressos/Coffee/Pastries, are generally pretty inexpensive in Italy at about 0,50€ - 1,50€. We never even tried paying for something that cheap with a credit card, and I don't think you should either.
We used a couple personal drivers, and they all only accepted cash.
In Venice and Amalfi there were many small vendors who didn't take credit cards, and many others required that you spend at least 10-20€ before they'd take credit.
In Rome we were able to use our credit card everywhere, however, we didn't make it to any of the Artisanal shops during our stay - but from what I've seen from the other places we visited, accepting credit cards would be pretty hit or miss. In Rome, there are TONS of street vendors selling art or selfie-sticks, and I highly doubt they accept credit.
In Paris we used our credit card everywhere and had one Cafe/Bar require we spend at least 10€ so we could use our credit card (we ran out of Euros). It is generally hard to spend less than 10€ in Paris anyway, though. haha.
When asking vendors if they accept credit cards sometimes we would get a question back asking if it was American Express; i'm not sure why they'd ask but my assumption was that not all of the vendors accepted it.
Unsolicited Advice Section:
Note: get a credit card that doesn't charge a Foreign Transaction Fee (which is usually around 3%). BarclayCardUS has a no annual contract card with 0 foreign transaction fees and a 25,000 point bonus for using it (which you can use on an travel related purchases - including Uber!). You also get extra points back on those travel purchases. The down side is that this card doesn't have a chip and pin, which I noticed frustrates the vendor sometimes. On one of our flights they accepted credit cards but ONLY with chip and pin, which I was told is common in Paris (but didn't experience myself)!
As for converting USD to Euros: we did it at a bank out of necessity/emergency and they charged us about 12%. I did notice that there are places that claim they don't take a commission; just make sure you know the exchange rate before you go that route to avoid getting ripped off.
Final note: others have already mentioned the pick-pockets, but I'd like to add that they can be a more brazen than what you see in the movies. One (elderly) family member had his man-purse ripped from his shoulder, and another had his cell phone swiped right from his hands. From what the locals tell me, that's about the worse things that happens in these touristy areas. So, hold on to your stuff tightly and put your valuables in your front pocket only!
Traveling to France (mostly Paris) and Italy (Rome, Venice, Sorrento)
I mostly pay my day-to-day expenses (local transport, lunch, souvenirs...) with cash.
Bigger expenses (mostly restaurants) with my Credit card.
I usually keep 60 to 100 euro with me all the time; I keep 20-ish euro in my front pocket and the rest in the wallet in my back pocket (not really paranoid).
I use the ATM when low on cash. ATM machine are directly usually on the street (even bank machine), just be more careful than usual, pick your cash and quickly put it away (pocket and/or wallet).
I leave the Credit card (and most of the cash) in the hotel room safe; and bring it only if I know I will use it.
In France, cards are widely accepted anywhere (and not more in Paris than in rural areas), but in small shops there's often a limit on the amount. In Paris the card is generally refused for anything less than 15€, sometimes 20€ but that's in extreme cases. In rural areas, the limit is more often around 10€.
I live in France, and I almost never carry more than 60€ on cash with me. That's enough to pay for small amounts at the bar or such things. Since you're a tourist, you'll probably make more small payments than I do daily, so might consider carrying more with you. I'd still advise to carry small cash amounts, and withdraw from an ATM when you need more. There is always one nearby in Paris.
I have only spent a few days in Rome, but I did what I'm advising you. I carried small amounts of cash for small expenses, and paid by card for restaurants, museums, etc...
Always have some cash on hand, enough to pay for the restaurant if they don't accept your cards or any cards at all. Spread the money among people in your travel group.
Warn your bank so they don't block your cards and bring two different cards if you have them (some circuits like american express aren't accepted everywhere, mastercard or visa are very widespread).
Paris and Rome are typical for pickpockets as are all touristy areas in big cities. Pay attention when withdrawing money from ATMs.
For small payments, using the card is more rare but if you ask they usually do it, in Italy forget about using credit cards for street food or even some small shops because many don't have a machine. Depending on the size of your group you need a minimum amount of cash because it can happen that some restaurant doesn't take credit cards, or doesn't have a working POS machine and you don't want to waste time looking for an ATM.
Are you coming from the US? Is your vacation date at least a few months in the future? If so, you might be able to save a little money by buying your euros now, or dollar-cost averaging them between now and the time you depart. The exchange rate is pretty favorable right now. It hasn't been this good in about ten years.
If you do this, you'll be paying for things in cash. You'll have extra motivation to pay in cash as opposed to plastic if the rate gets less favorable during your vacation.