I think three groups should go, four would probably be too much, but there are four statues
Caves, Lake and Gate.
Caves (may be primary melee) may be easier at the start (kobolds), but may be harder if they are in kahoots with the Cult - or at least make it harder to get out that way.
I guess someone with intimidate, persuasion and trap detection (kobolds!!) should be there. I may go and stalk the kobolds, imagine the terror if someone start negotiating and then someone in the background just dies or collapses with no discernible source
Lake: people who can swim obviously, no heavy armor.
Gate: face people with ranged support
I nominate myself for the Caves.
Ambush: as many of us as can be. Assuming the main driver in the caravan is the cultist, someone who can change shape/disguise should go (gloomstalkers both can, but neither is good at deception

)