Are there any names other than [name_f]Gracelyn[/name_f] and [name_f]Graciela[/name_f] that [name_f]Grace[/name_f] could be a nn for?
I would go straight to [name_f]Grace[/name_f]. It is a beautiful, perfectly legitimate name so I don’t know why you would want to use it as a nickname?
[name_m]Grayson[/name_m] would be a more unisex choice, but I too like [name_f]Grace[/name_f] as a standalone name.