I love [name_f]Petra[/name_f]. I really love [name_f]Apolline[/name_f] (and your reasons for using it)! I’m less excited about [name_f]Joy[/name_f], but I do see how it works perfectly in this combo. And I like the shared meaning with your boys’ middles.
It does seem lighter and happier than [name_f]Petra[/name_f] [name_f]Antigone[/name_f] [name_u]Jule[/name_u].
You can’t help but smile when you say it. 
I honestly can’t decide yet which [name_f]Petra[/name_f] pairing I prefer because they feel so different.
I suppose the deciding factor will be whether to honor the Pauls and Paulines or whether to honor [name_u]Jule[/name_u].
I agree that [name_u]Jule[/name_u] goes better with [name_f]Antigone[/name_f] than [name_f]Apolline[/name_f].