So I actually had Urgala step in and give a bunch of knowledge on giants (we came out of LMoP so we skipped chapter 1). I had her tell them that in all of her adventuring days she had never encountered fire giants so something serious must be happening for them to be leaving their city. She offered to take the rod of the Vonindod and have a wizard do a detection ritual on it to find out what was going on, and said in the meantime if the players wanted, they could go visit her friend who has a giant slaying weapon if they would like to pursue the giants. So now their main goal is to go get that and then come back later, but my plan is to have them meet Harshnag before they return