That works for me! Penelope will definitely ask Crow about why he's eating so little so Gavin could potentially over hear that too so it adds to the suspicion of when he finds the rest of it. Maybe a couple other small things too could lead to him being suspicious enough to follow Crow cx 
Also I totally forgot but were we going to have Gavin convince Penelope to go with him when he follows Crow? xD [s]so many plans I lost track lol[/s] I figure he could start pestering her about suspecting something is up and of course, she won't take him seriously so when he decides to follow Crow, he could bother her enough to go just to prove him wrong xD 

Yeah that sounds good c: