[X] The one which is practically the entrance to a cave
Little info to go on here. Thought the big cave does not sound like that great of a place if we want out of here, thought if we explore it and tag it with an Ofuda it could become an excellent base of operation and/or retreat point. I am willing to go explore that area for this as well as by time for Zelkova to wake up so that they can leave this place. Just remember to mark our path so that we can get back here later.
Thought I have to say exploring that third option just to know what it is, also works for me. Upstream option might be the way out but I rather leave this place only after Shinji and Zelkova are both ready.