Starting undermountain, would like advice

[Efrate]

Hello Giant.

A buddy is going to be running the FR campaign Undermountain, and I am at a loss as to what to play. I know only a bit of lore surrounding it as I've run FR stuff before, but without spoilers, I was wondering what to run within the party to have a reasonable chance of overcoming challenges therein. I assume it was written with the standard Fighter/Rogue/Wizard/Cleric in mind.

Allowed: Core, Completes (not psionic), UA and Dragon Compendium maybe/maybe not, case by case, but likely not, most FR specific stuff, ToB (but not RKV), Draconomicon, Dragon magic, Heroes of battle, SpC

Not allowed: Anything psionic, incarnum, anything eberon, anything from another campaign setting and/or adventure specific, Tome of Magic, Dungeonscape, most stuff not listed. No prestige classes, items, etc. will be refluffed, if you have to worship Pelor it is off the table. Don't be a pain, don't be pun pun, don't invalidate the party.

Specifically, I cannot be a Factotum, an archivist, an RKV (mentioned twice, DM hates the class and what I could do with it).

T3/4 at best is what I am guessing.

What we have:

Melee type, likely barbarian or fighter, almost stictly core. New player, just wants to hit stuff and do nothing else.

Eldritch Theurge: Utility invocation and spells, and blastiness. Lots of blastiness.

Arcane Caster: Some kind, one player always plays one. Usually summoner, otherwise Ultimate Magus. Wizard guaranteed, other stuff maybe.

ToB Something: One person is definitely playing crusader, warblade, or swordsage. Or he will when whatever he first chooses dies horribly for him being an idiot. Sadly its a pattern that happens continuously.

Me:...? We Need a skill class, and a divine caster. We also have no party face for interaction with skullport/anyone. I am not sure how important a face may or may not be, anyone give me an idea?
Also for divine caster, is there a divine caster with trapfinding, and not the summon celestial monkey kind. I know it will be needed. And I doubt I'll be able to somehow justify the kobald domain. Is there a weird cleric alternate that lets me be more of a skill class? Also cloistered is almost certainly out, and it is almost certain if I do go cleric that I will have to be of a deity in Faerun that makes sense, not just grab useful domains. DMM is also off the table.

I'm most leaning towards druid and trying not to break it, but that does leave us short a skill class and/or a face. Beguiler was another option but that leaves us without any divine casting. I suppose our theurge can UMD lesser vigor wands but still. Dread necro sounds fun but I know for a fact I won't have access to any reasonable corpses, any undead I create will be unable to create spawn, and any incorporeal undead get hurt by anything with dr/magic not just manufactured weapons. Bard was the other option, giving a bit of everything, and might be what I come down on but it just feels kind of meh.

tl;dr Without spoilers is a face needed in undermountain? How important is divine casting vs. skill monkey? Any class that does both dececntly?

[ComaVision]

Think you have enough restrictions?

A Ranger can use Cure wands and can trade out Track for Trapfinding (that's Dungeonscape though, which I didn't see in your approved list).

Alternatively, a Swift Hunter (feat) would have trapfinding, though you might need to pick up the Able Learner feat to cover your bases.

There are some Rogue/Cleric prestige classes that progress spellcasting and sneak attack as well.