Student tour to eastern Europe

My grandson just returned from a High School trip to France (12 days). All his meals were included. He had a card to use for purchases. He took $100 in euros and came back with $80. I would think your son would use the card more then cash for lunch. Not exactly answering your question! I would think 20 euros a day would be more than enough. Hope he has a fantastic time! My grandson flew over with a group. They flew back in groups of 3 or 4 students. Amazing he lost nothing.

There is too much variation in pricing to say definitively (depends on the restaurant, whether it includes alcohol, type of food ordered, etc.)...but in general, these places you mentioned are not expensive so I would not stress over budgeting (think of it like lunch in the US, except cheaper). To give you a straightforward answer, don't exchange anything, there is no need. An ATM card tied to a checking account is the best way to withdraw small amounts of cash in each country. No need to overthink this. I'm not sure what a "card with money on it" is, but I hope it's not some pre-paid card that would face difficulties being accepted overseas. I would ditch that idea and keep it simple with an ATM card (get one with low fees - I have a credit union card that charges 1% of every transaction) and a credit card with no foreign fees (Capital One, etc).

1000 forint in Budapest obviously won't be enough. It's less than $4.

I want to second what Agnes said about pre-loaded cash cards. Many of those come with horrendous charges (to set up, to withdraw money, to add money, etc.), and they often simply do not work at all. There is not much that is more confounding than getting to Europe and finding out that your planned source of funds isn't going to work for you.

He needs an ATM card. If he has that (he doesn't lose it, it isn't stolen, and the issuer doesn't block it for some reason), he can get by without a credit card, but I would want to have both.

Enroll your son on your ATM/debit card and get him a copy. He can take out money when he arrives and spend it, cheaper than trying to put every little purchase on plastic (and cheaper than trying to buy currency at home.) When he returns he will want his own. Review the account with him first, then negotiate.

These websites can be useful for Polish part of the travel
http://poland100bestrestaurants.pl/en/
https://www.tripadvisor.com/Restaurants-g274723-Poland.html
http://www.bbc.co.uk/languages/polish/soap/facts.shtml

Put the PIN into his phone. Get a money belt. Go over the "tourist drill" - passport in the money belt, credit card there too. Give him the credit card today, and get him to make some purchases.

In terms of the phone, make sure that he knows that the phone should NOT be kept in the same way as in the US. Roaming charges can be very high. Just texting away out in the open can be expensive. He should be in airplane mode with WIFI off. He should only text when inside a wifi zone, like in the hotel. He would turn WIFI on, and then text as needed. He should not call on the phone at all - of course, kids don't do that anyway. If I was the parent, I would carefully monitor plan usage while he was in Europe, and send a quick email/text if the data usage explodes.