How would Peter know where to find Voldemort?
In canon, he knows because Harry, who was regrowing his bones in the infirmary, overheard Dumbledore telling McGonagall where Voldemort was, and told Ron what he heard, and was overheard by Scabbers.
But, unless I'mmistake, this hasn't happened in your story, so how would Wormtail know where his master is any more than any other Death Eater?
First, Harry assumes Wormie is off to find Moldie Voldie because that's what he did in the originally timeline. Is that what he'll do in this one? Probably. Why? For a lack of a better idea. ~Jeff~