[name]John[/name] [name]Dominic[/name] nn [name]Jack[/name] & [name]Mary[/name] [name]Abigail[/name] nn [name]Molly[/name]
[name]Jack[/name] and [name]Molly[/name] are names in their own right, these days. If you really like those names and plan to call your children by them, then why give your children names like [name]John[/name] and [name]Mary[/name] that you have no intention of using? Unless, of course, you’re naming them after a relative or something.
I like [name]Jack[/name] [name]Dominic[/name] and [name]Molly[/name] [name]Abigail[/name] just fine.
– [name]Nephele[/name]
I second [name]Nephele[/name]'s opinion, unless [name]John[/name] and [name]Mary[/name] are to honor someone or given for religious reasons.
I actually prefer the more formal, starchy [name]John[/name] and [name]Mary[/name] to [name]Jack[/name] and [name]Molly[/name]. They somehow seem more solid to me. The names and nicknames are great though, strong, classic names with cute short forms.
I think they’re great combos, and I love [name]Mary[/name] paired with [name]Abigail[/name], as it feels unexpected to me.
Good luck! 
I love [name]Molly[/name] and [name]Jack[/name], and also [name]Dominic[/name]. However I agree that [name]Jack[/name] and [name]Molly[/name] are fine to use as first names, and that this would perhaps be a better option unless [name]John[/name] and [name]Mary[/name] are honouring relatives.
I actually happen to know a [name]John[/name] [name]Dominic[/name], who goes by his middle name, and I do like the way this combo sounds.