[maybe it's symbolism!! but when Charon takes a seat he might get a clue: it feels restful to sit on this couch. it isn't an immediate effect, but there is the sense that he's regaining energy as he sits.

instead of going to get any drinks, Lethe squishes onto the couch right up next to Charon. with a wave of his hand some drinks appear on the table--warm tea, coffee, water, juice, and soda]

It's no trouble, see? Pick whatever you'd like. What are you doing here?