Even if they'd for sure get out of the ravine if they had all day I'd still make someone roll for the party as a guide to how long it took them and-or how many of them got hurt in the process.
Roll a 20, they scamper out within 15 minutes none the worse for wear and can spend the rest of the day doing whatever they like.
Roll a 1, they spend all day at it and finally crawl out long after nightfall, exhausted. Further, each of them now have to roll individually to see how much damage they took from scrapes and falls in the process, with anything over about 14 meaning none but a 1 meaning (in 5e) we might be looking at death saves.