I prefer the EVE-lyn pronunciation for a girl and EV-uh-lyn/EV-lyn (the way I say it is a cross between the two) for a boy (as I like the name for both) simply because
EVE- seems much more feminine than EV- does.
Other nicknames:
EveEvaEvvie (EV-ee rather than EVE-ee)
Ev
Lyn