This trial is testing a psilocybin-based treatment to help patients with inoperable pancreas or biliary tract cancers feel less distressed. Psilocybin, found in certain mushrooms, can change brain activity to improve mood and reduce anxiety. The study will also look at how this treatment affects patients' families. Psilocybin has been historically used for ritualistic, recreational, and medicinal purposes, with recent studies recognizing its potential to treat depression and anxiety.