I too think Susanna(h) is the perfect fit! [name_m]Bright[/name_m], summery, old-school sweet, slightly [name_m]Southern[/name_m] [name_f]Belle[/name_f] vibe.
I also like [name_f]Fern[/name_f] and [name_m]Darcey[/name_m] for you, in that order. How about [name_f]Georgia[/name_f], [name_f]Delaney[/name_f] or [name_f]Helena[/name_f]?