I would suggest saying a prayer and leaving it in peace.
Are there any markings on the stone?
After that, Mulligan will head back to the junction and head down the main passageway to see what is there.
Agreed, I don’t like the idea of disturbing a grave. It gives me the willies, and I don’t willie easily.
Are we tasked with completely clearing this place out of potential threats? If so, I think we should leave no stone unturned.
And the same can be said for the undead.
I’m fine with leaving it if we’re sure that whatever’s in there is unlikely to be disturbed anytime in the distant future.
Is there anything noteworthy about the stone when looking at it closely?
The task it to destroy as many organized pockets goblins and undead as possible. The final thorough cleansing will take months or years and the Dwarves plan to complete it. So you can leave stones unturned or leave them for later.
There is nothing note worthy about the stone accept it was very well made.
Then Bitur is fine with whatever the rest of the party wants to do (which seems to be leaving it undisturbed). After all, I don’t think it’s going anywhere anyway.
Mulligan finds the passage come to a better lit T-intersection. This passage runs a distance each way and has 3 torches lighting it. There are many passages coming off of it.
Do you investigate the first room with better lighting?
Why not 
The other small chamber is very similar to the one explored. It is slightly oval, has smooth walls and a 4’ x 7’ grave cover slab. This one looks like someone long ago tried to break into it. A large chunk has been chiseled out of one corner and it appears the slab is 6" thick. No evil is detected and no traps were found.
You know, I wouldn’t want to leave any foes at our rear. I think we ought to at least peek under any slab, and into any tomb, we find, if we can do so easily. Gilraen or Hraedsig can then re-sanctify them, if necessary. Remember that the passageways seemed to be crude and goblin-made, but these slabs indicate a higher level of stoneworking skill. What did this place use to be? We might need to know.
Elfstan adds a quick agreement to the Sea Knight’s words. He hates the thought of another wight sneaking up behind them. He is however somewhat comforted that he is unlikely to be in the rear. 
Agreed, but the key word is “easily”. Let’s assume that any weighty, well-fitting, well-sealed slab is probably beyond the powers of what’s under it to shift it, and simply make a note of its presence (unless Gilraen or Hraedsig are given any signs by the Valar).
So the party heads to the T intersection. Going left is slightly angled and a torch dimly lights a chamber 30 or 40 feet away. The other side runs about 60’ with two torches and curves away.
Let’s go back just to check the two slabs we already noticed. Would the Dwarves please determine, can they be easily lifted?
Hraedsig is opposed to desecrating graves willy-nilly, but there should be an easy way around it. Any undead located within should be able to be Detected without moving any heavy stones. If anything is detected, then further investigation would be warranted.
Hraedsig is being quite reasonable and he specifically did not detect evil so the chance of undead being beneath is minimal.
Bitur thinks it be worth it to check a bit down each passage of the T-intersection first again as Elfstan and Mulligan did last time, but this time, unless absolute stealth is an issue, which it probably isn’t, seeing as how undead don’t really see and hear as far as he knows, the scouts might want some heavy backup.
You know, given that we came through the Grave door, we are likely to encounter a LOT of graves, as this was probably the burial exit for which ever tribes lived down here. I think desecrating each grave we come across in the name of “making sure” is likely to make us more enemies regardless of a consecration afterwards.
Elfstan, you check the 30’-40’ foot passage and peek in to the room. I’ll check the other way with two torches to the bend.
Bitur, no offence, but anything and everything, dead or alive, can hear you and Gwaelur coming. Don’t worry though, we’ll stay within sight of the party. 
Ghân (‘Skeleton-killer’) can Stone Shape the tombs to seal them, if desired.
Gilraen to Ghân, “I think we must be careful in marshalling our spells. We will probably be in here for a long time and the party or even others may need our spells more for bigger threats and serious injuries.”
The party moves up to the intersection.
Elfstan goes to the left (east) and see a large chamber lit by a single torch with a large pile of rubble across the chamber. It also has a door on the west corner. The room is a roughly rectangular shape but at about a 30° angle placing the door actually to the west of the long passage the party came up. The room is roughly 70’ from east to west corners. It is dirty and rough hewn but currently empty. Checking the door is not locked and does not seem to be trapped.
Mulligan heads west passing the torches. The passage runs about 100’ curving sharply north to a very odd shaped room that is roughly 45’ (east/west) x75’ (north/south) but with rock juttings into the room. It appears to have been a natural chamber poorly enlarged. On the north wall are two doors and in the room there is 6 goblins. All are geared for battle and from their harsh language appear tense about the Dwarves and their plans for a siege.
No offense taken. My point was simply that stealth doesn’t count for much against beings that don’t really see or hear in the traditional sense anyway.