What should one do who made a vow to honor two friends in another country if it is impossible to fulfill the vow due to the distance and difficulty of reaching them?

If you vowed to honor your two friends upon the occurrence of a certain event, and that event has not yet occurred, then nothing is binding upon you. However, if it does occur, you are obligated to fulfill your vow by exerting your utmost effort to deliver the honor to them by any means. Remember that a vow is not binding unless it is uttered verbally; mere intention is not sufficient.