A "reunion" is a meeting for business purposes, a "cita" is usually for appointments, and "mitin," for those of you who didn't know it, has the purpose of expressly indicating a political purpose for a congregation of people. The word "reunion" in English is a special kind of event where people who haven't seen each other for a long time get together. It can be former university colleagues, former business associates, but it is especially family members, including aunts, uncles, cousins, and other associated kin who get together and have a picnic, or a "merienda campestre," and spend time catching up on the events of each other's lives.
However, I have a small issue with the use of the definite article "the" as being mandatory. In regular use in business we say "at meetings," which is to talk about customary and habitual actions or practices that occur therein.
I got dinged for using "one another" instead of "each other." I reported it.
"Each other" and "one another" are equivalent in modern English.
I was taught that "each other" refers to two people (or ring-tailed lemurs or whatever), and "one another" to a group of three or more, but that distinction has disappeared in general use.
In this example, we don't know how many people are involved, so either answer is correct, even if you follow the old rule.
There are many, many sources on the Web to back me up. Here's one: