I was thinking emma stone as molly and the guy who plays oliver queen in arrow as harry. hes not quite tall enough but if you could get him to crack a joke he has the right look.
I was actually thinking about Stephen Amell for Thomas, based entirely on the fact that he is so pretty. Colton Haynes works well, too. (And, in a trippy meta-feedback loop, Paul Blackthorne as Malcolm!)
Also, while we're mining
Arrow, John Barrowman as Lord Raith, Cynthia Addai-Robinson as Gard, Carlos Valdes as Ramirez.