More specific to your request for information other than the recommended "just totally prepare", all food and beverage is buy-on-board for the US-Iceland and Iceland-Europe segments in Y.
Use the Information link on their website for menu's and pricing.
offers a wide choice of food outlets, so maybe consider eating your dinner at the airport and enjoy a beverage or snack on the aircraft. Bring along some snacks (almonds are great washed down with a cold beer or glass of wine) but enjoy a nice meal in the terminal if you're hesitant to consider purchasing a meal on board. You should have time and opportunity to purchase food in KEF
during your stop - coffee, sandwiches, and pastries are very good and reasonably priced.
Take the train from Schipol to Centraal Station to get into the heart of AMS
easily, and a fun way to get around is to use the "Canal Bus" instead of just relying on the trams...or your feet. It is a hop-on, hop off service and you can purchase multi-day passes that includes unlimited use of the trams as well. A gazillion bikes to rent as well, but learn the "rules of the road" first for bike use.
can be pricey, but great food and very nice people make it a great city in Europe to visit.
Good Luck and Safe Travel,
watch what you want. you may get it.