The scenario that would be the most problematic, considering the limited usage of the euro, is:
A Danish family attempts to pay for their meal at an Italian restaurant in Sicily.
This is problematic because Denmark does not use the euro as its currency; it uses the Danish krone. Therefore, the Danish family may struggle to pay for their meal, as the restaurant is likely to prefer payment in euros, which could lead to complications with currency exchange or acceptance. In contrast, the other scenarios involve countries that are part of the eurozone or have a more common acceptance of euros (like Germany and France, both of which use the euro).