Café (with the 'é' instead of 'e') is the way the word is spelled all across the globe. While most people don't use the é and write "Cafe" instead of "Café", the correct dictionary word is still Café
A very very common word. Its been passed around so many languages...the Spanish use Caféteria, and Café itself has become an English word due to so much use.
I don't know about IDN values (don't own one, never seen one sold), but this is a very very good name with a massive appeal...