Scavenger Hunt incomplete

I did not complete the Scavenger Hunt (no Apple Cider then), but I did the Battle for LA and have gone to the point of reuniting Gwen and Keiran at Anvil Rock. The quest is still in my quest book and its says I cannot abandon it. What do I do now as Keiran is no longer outside the EoTN? Will it effect my future game play?

I would suggest trying to tag along with someone who hasn't done Battle for LA yet but has done the scavenger hunt lead-in dialogues. That should let him spawn so that you can give him the items if you care about completing the quest.

You don't have to finish the scavenger hunt to continue in the WiK storyline. just have to see all the dialogues before that. Also by the state at this time you didn't have to finish that quest for anything it only gives some mediocre presents which aren't worth your time.