I am a first time DM and ran this adventure tonight for three level 2 players - 1 experienced halfling cleric and 2 with less experience at D&D (drow rogue and tiefling warlock). It went great!
Since we were just running it as a one-shot I gave everyone an option of having a backstory that gave them a connection to Landy. I gave them a few to choose from and it worked out that the halfling cleric was Landy's protective adventurer cousin, the tiefling warlock was a fellow scholar who had been invited to join the expedition, but was delayed in her journey and was only arriving now, and the drow rogue (Charlatan background) was a spy sent to retrieve any powerful artifacts recovered by Landy's group. (The drow approached Landy in the inn while Landy was briefing her cousin and colleage and offered her services as mercenary/bodyguard, and was hired by Landy to accompany them.)
It went great! When they arrived at the tavern they didn't go inside, but hung around outside the door taking potshots at the goblins and then ducking into cover. I had been a little worried about killing anyone too early, so I split the goblins into 2 parties of 3 and rolled initiative for each, so that I wouldn't be put in the position of possibly having to have all 6 goblins attack 1 party member. They killed 2 very quickly without taking ANY damage by refusing to go in the tavern, so I had two of the remaining goblins run off to retrieve the hobgoblin, who put up more of a fight and nearly killed the drow. Once the hobgoblin was unconscious they tied her up, healed her and the tiefling quickly used "charm person" to determine that the goblins hadn't killed everyone and didn't know anything, and the party let them leave with the tavern's lockbox without even considering taking it themselves (although the drow did take the hobgoblin's longbow, and stealthily loot the other bodies.)
They took a short rest at the tavern and proceeded to the temple. They fought three ghouls in the main room; I put one in each chamber and one hiding by the entrance; they missed that one and were flanked by it after they roused the two in the side chambers. At one point our halfling cleric was flanked on either side by ghouls trying to bite attack her, one after the other, and both missed! I thought the chambers were very easy to draw on my battle map and the pillars were a nice environment to fight in.
Although Landy tried to encourage them to go down into the cavern right away, they didn't bother searching the rest of the room, but retreated to the surface, built a bonfire at the mouth of the entrance, and took a long rest instead. In the morning they searched around, found the bowls and equipment, but were very wary about doing anything with them that might be a necromantic ritual or call on dark powers. What if they got turned into ghouls? If I was running the adventure again I might make the journal entry hint at hidden passages, or add an inscription to the front of the altar, something like "show that you are knowledgeable and worthy to open the way" to make it clearer that there is some kind of hidden passage around. Or maybe more experienced players would have found the hidden door already? The Tiefling rolled a 20 investigation so I just told her flat out, well... three bowls, three offerings, two doors... Once told what to look for, the rogue managed to find the door. Everyone was STILL too scared to do the ritual, so finally Landy did it.
By this point they all had discussed it amongst themselves in character and decided "It's definitely Calador. He's the evil one." Landy resisted that conclusion but eventually admitted it might be true. Not sure how I could have kept that as more of a mystery.
Anyway, they met Calador, he got out about one sentence of "thank goodness you're here" before the tiefling cast Charm Person again; even with advantage he failed and gladly admitted that he was a necromancer and invited everyone to join him in his quest for power. They knew Charm Person would fail when they attacked him, so the rogue snuck around behind and sneak attacked him, doing something like 15 damage immediately.
They fought Calador (I goofed up and had his AC at 15 to start with, without casting Mage Armor, and didn't realize for a few turns, so to make up for that I crossed out Shield & Magic Missile and didn't let him cast those.) The drow knocked him unconscious the first time and he revived, which everyone thought was a very cool effect. He then firebolted Landy into unconsciousness, which upset everyone - even the drow had become fond of her and wanted to really protect her. Again, the tiefling got a nat 20 arcana check and I advised the bone would be vulnerable to radiant damage. The cleric destroyed it on her next turn, and the tiefling got the killing blow on Calador.
I put in some secret necromantic texts in Calador's pack for the drow to take back to her spy organization, and the team carried Landy out and stabilized her. It was very sweet, when she announced her intention to become an adventurer and fight evil, they tried to talk her down and convince her that scholars were also important and that she shouldn't give up on her dream of being an archaeologist. Landy said she could do both, like her colleague the tiefling, and she wasn't giving up on her dream, but she also wanted to be able to protect people. We ended there. All in all the session took about 4.5 hours, I felt like it moved pretty swiftly considering the drow and tiefling players weren't that experienced with 5e. Thanks so much for a great adventure!