With your sibset I would do [name_m]Sebastien[/name_m] but I love all of your options. In order I would say:
[name_f][/name_f][name_m]Sebastien[/name_m]
[name_f][/name_f][name_m]Wilbur[/name_m] (this has really been growing on me, it’s so cute)
[name_f][/name_f][name_m]Bastien[/name_m]
[name_f][/name_f][name_m]Etienne[/name_m]
One other suggestion would be: [name_m]Elliott[/name_m]