It is too soon. In the honeymoon for visitors. Nicolas may be Marcos best friend, but friends do not belong in this instance.
How many days would be acceptable? Ten? Easy fix.
When ever the honeymoon is considered to be finished. Probably after the couples have returned home.
There is a very specific reason why they HAVE to meet up in Puerto Aventuras and it affects the entire rest of the series. I don't mind changing the number of days, but they have to have dinner together at that exact spot while on their honeymoons. Like I said, that moment changes the course of the whole series.
See, thats where you have a definite advantage, you know where any event is leading. I just thought that it sounds strange to meet up 6 friends on your honeymoon. By the way, I have enjoyed the story thus far. You have a special style for developing interest in the characters.