My instinct goes immediately towards [name_f]Rosemary[/name_f] [name_f]Julia[/name_f]. I was a big fan of [name_f]Julia[/name_f] when you were considering it as a first name. I really like the cleaner, tailored feel of it which I also get from [name_f]Anne[/name_f].
I would also be more moved to use your mum’s name as I assume your family uses your husband’s surname. [name_m]The[/name_m] use of someone’s first name also feels more significant as an honour name compared to someone’s middle name.
[name_f]Rosemary[/name_f] [name_f]Louise[/name_f] works well together since it flows in a more predictable way with the 3-2 syllable pattern. But I do find [name_f]Louise[/name_f] more expected as a middle in general, as well as with [name_f]Rosemary[/name_f]. [name_f]Julia[/name_f] is less expected, not near the level of McCall but I find it more refreshing. [name_m]The[/name_m] 3-3 syllable pattern of [name_f]Rosemary[/name_f] [name_f]Julia[/name_f] sounds nice because they don’t have the same rhythm, and [name_f]Julia[/name_f] sounds quite uplifting next to a 1 syllable surname.
[name_f]Rosemary[/name_f] [name_f]Lou[/name_f], [name_f]Rosie[/name_f] [name_f]Lou[/name_f], [name_f]Marylou[/name_f] are all sweet established nicknames but I think [name_f]Rosemary[/name_f] [name_f]Julia[/name_f] could lead to some more distinctive nicknames to go with McCall ‘Mackie’. E.g. [name_f]Mary[/name_f] [name_m]Jay[/name_m], [name_f]Mary[/name_f] [name_m]Jules[/name_m], [name_f]Rosalie[/name_f].
I think if your sons had very traditional middles names like [name_m]James[/name_m], [name_m]John[/name_m], [name_m]Thomas[/name_m] then [name_f]Louise[/name_f] would be the most cohesive pick, but your middle names are not expected so from that perspective I like [name_f]Julia[/name_f] best too.
Again, all the best with your final decision!