I think it's interesting that the trap creates an illusion of an ideal results for the Order. Belkar ends up dead (and is clearly affected by the trap in the last panel). I don't think their illusionary reality is consensus either... the Belkar's graveside panel- Elan and Haley are grieving (and Roy isn't). I don't think Roy (or Haley really) would be especially keen on Elan coming to terms with his brother and father or riding a dinosaur so it's probably not just taking the 'happy ending' from one mind.
Rich generally does pay subtle attention to the details\internal logic (and foreshadow, though sometimes not so subtly), so is the 'happy ending' a result of the spell deciding <this is the ideal end result> or that Belkar's (and Mr. Scruffy's) desired happy ending conflicted with the others? Or does Belkar have a pretty strong deathwish?