One way to do this mechanically is via the Help action

From "working together" in the Basic Rules (p. 59) you can apply advantage without resorting to anything "custom" to the adventure.

Working Together

The character who’s leading the effort—or the one with the highest ability modifier—can make an ability check with advantage, reflecting the help provided by the other characters.

A character can only provide help if the task is one that he or she could attempt alone. For example, trying to open a lock requires proficiency with thieves’ tools, so a character who lacks that proficiency can’t help another

One way to tailor this to the published adventure is that whomever has the highest Wisdom modifier tries to navigate, and the guide helps. Or, because they are not familiar with Chult, you make a group check (basic rules, p. 59) with advantage because the guide helps.

• You could make a ruling that unless the Wisdom(Survival) attempt, or help, is made by a character with proficiency in (Survival), but that's somewhat beyond the general theme behind ability checks: you can try anything, you'll have more chances of success if you are proficient.

You only need to roll the ability check if the outcome is in doubt.

Caveat: most of Chult is unexplored and poorly mapped. Most of the time, you can expect there to be some uncertainty, as described on pages 38 and 39 of the book, sections on the Land of Chult and Navigation. There are some NPC's whose back story includes being very familiar with a particular area, however, in the interest of avoiding spoilers, I'll get no more specific than that.

Guidance versus Guides

If the party has a Cleric or Duid, the guidance cantrip is a handy way to increase the chance that the party Navigator, be it Guide or PC, has an increased chance to not get lost/head in the right direction.

Nothing, mechanically

The ingame map, as it's introduced in the book, does absolutely nothing for your players in terms of navigation, other than allowing them to point to where they want to go in the first place.

My players too complained that the guide isn't particularly useful, because their own survival check was higher than that of the NPC guide they had along. They continued to complain about how useless their guide was, until they got seperated from the guide and suddenly couldn't figure out what jungle food was edible, didn't have somebody to tell them the customs of the Batari Goblins and didn't know what direction locations not on their map were.

If your players complain that the map isn't useful, simply take the map aspect away, it's not truly needed.

If you want to keep using the map but they complain it doesn't help them, take the map away for a second and ask them which direction they need to go to reach the Peaks of Flame and Smoke from their current location, making a stop for supplies at Camp Vengeance. Suddenly a map doesn't sound quite as useless, because a map helps you know -where- you want to go, while navigation checks handle the -how- you get there.

Travel in the jungle isn't difficult because you don't know where you are going, but because it's simply not always possible or feasible to take the direct route. Trying to take a shortcut and ending up on the wrong tile because of a bad roll is easily described as the forest looping around and leading to a dead end, map or no map.