Alright, since Tanthalus was lucky enough to not fall onto a mushroom, he is quite safe now. Here's how I see things going down.
In the game thread, I had Shandien ask Tanthalus for confirmation of his well-being. If it is not confirmed, i.e. either Tanthalus does not answer or answers negatively, Shandien will backtrack to the first pit and lower a rope. If Tanthalus expresses that he is well, then Shandien is going to suggest that Tanthalus runs to the bottom of the second pit where he will lower a rope, or Tanthalus could suggest this himself.
The benefit of the second option is the exemption from any more Jump check for Tanthalus. The disadvantage, of course, is if Shandien falls into the second pit, at which point, I guess, Galadren will have to do something about that. I actually had this in mind during the first fall, but I thought it would be too out of character to abandon chasing the goblin without knowing where he was going.
P.S. The thing is though, I only need to roll a 3 or higher to clear the pit. Falling the first time was very unlucky.