Feather Fall Spell in 5E – Target Validity Issues?

Couldn’t find an answer to this in my reading of the source books nor on stackexchange. My players were engaged in an encounter in which enemies were able to manipulate air to "gust" them off a cliff. They did recognize that they needed to stay away from the edges but started to lose the battle because of pretty sour rolls. They decided they would leap from the cliff knowing that the sorcerer had the Feather Fall spell.

Feather Fall states: "Choose up to five falling creatures within range. A falling creature’s rate of descent slows to 60 feet per round until the spell ends. If the creature lands before the spell ends, it takes no falling damage and can land on its feet, and the spell ends for that creature."

Because of this targeting restriction, the spell could not be cast unless someone was already falling. As this takes a reaction, there seems to be no way to (prophylactically or otherwise) have the group under the spell if they all decided to jump in the same round of combat. In fact, it seems like it would take 5 castings (party of 5) over a series of 4 or 5 rounds to effect this strategy (with the sorcerer going last), which meant certain doom. I decided to call the session (it was time) to give me a little time to investigate this, but I basically told them there was no way I could see saving the party via feather fall. They were quite dejected considering they/he thought that Feather Fall could be cast as a proactive spell so that they could all jump safely on their own turn.

Can I confidently confirm that I have interpreted this right, whether RAW or RAI?