Had the second session of the campaign yesterday. We are now at five people, which was fine - GB, MM, Mal, and min maxer 2 (MM2) and Shar. (MM and MM2 are not really bad min-maxers, but I'm sticking with the format.) The order in which people showed up basically meant we ended up with two people independently wandering into the dungeon the first three were in - I would have preferred working it in as a story, but it would have wasted a lot of time.
It became clear that GB is not going to be as engaged as everyone else. When they are searching things, he stands guard or patrols. So I gave him the responsibility of mapping everything. His character has cartography, and he had said he was mapping something before, so he has the job. I described, he mapped, and when they prepared to leave, I had him make a cartography check. He got a 12, so I pointed out a couple, but not all, of the errors, had them take a picture, then wiped for the next floor. Made things a lot faster, and I think he was pretty happy with it. I'm learning Inkarnate, and making some nice maps for him to have a kind of reward for it.
Mal wants to range, so he actually helps speed things along. MM, MM2, and Shar all want to discuss anything they find in minute detail. As they talk, I ask anyone not part of the discussion for any actions. As GB continues to stand guard, Mal decides he's not waiting around for this and starts to explore. When the three deep discussion people notice the ranger wandering off down the hall, they get back on track.
I also improved my skills with running things. D&D Beyond has become a really useful tool - I have one browser open with a tab for each character, another open with a tab for the encounters I have saved, a combat tracker, and various notes, then I have the maps available on my tablet so I can always scan through them. With the character sheets in front of me, I can generally access info on the characters as quick or quicker than they can.
Even with all that, it still took the entire session to finish up where I thought the first session would get to - and that only happened because Mal and his leopard knew that it was getting late in the day. Then they all remembered the quest hook from town, and made a beeline for the exit. They never even went into the caverns! I believe this means I just have to double my expected time to get through an adventure.