In this sentence, i understand that the meaning is “we got into an argument when deciding where to go for a honeymoon.”
What is the function of 而 and 為咗？
[為咗 A 而 B] = [ to B for A]. It is a two parts function word for "for "
[(為咗) cause (而) verb] = [verb (for) cause]
"(為咗)钱(而)工作" = "work (for) money"
[我哋(為咗)決定去邊度度蜜月(而)閙交] = [we (to) quarrel (for) deciding where to go to have honeymoon]
In English, we have to omit "to" before the verb if there's a subject in the sentence , e.g. "to work for money" --> "I work for money". but we don't omit "而" in "我為咗钱而工作" in Chinese, because [為咗 cause 而 verb] is a set structure.