If Trevor can't make it then we could e. g. do Vale quests with Corwin's bard, your fighter, Jm's artificer and my cleric. We can get 2 hirelings to help us. We just have to check if all of us can do Vale and still get bravery bonus.

We just make a decision when we see who will show up. I think we don't have to have a completely full group with the mid levels to play them. Cm can e. g. play with Az or some of you to get some XP. She could even solo with a cleric hireling lower level quests. The only area we should not advance with a less than full group is quest chains we run. It's not fun getting out of sync because one couldn't join a session. It can happen to all of us.

If we run the desert with the mid levels we can focus on explorers, rares and the not flagging quests.