When I think about sib-sets, I tend to prefer combos that either both/all are longer names with shorter nicknames, or that neither/none of them do. It causes me a lot of grief, because my favorite girl names tend to be long ones with a lot of nickname potential, but my favorite boy name are typically shorter and do not have nicknames. Is this just me being totally anal retentive/type A? Or is there some credence? When I call all my children, will it be weird if only one has a nickname name and the rest have only full names? Why am I so neurotic??? 
Am I in good company here?
I understand your concern for uniformity in a sib-set, but I guess you might be a tad bit neurotic. It isn’t any big deal either way, though, but I’ll provide some sibling sets - with and without nicknames - for your perusal…
From my family, my name is [name]Lauren[/name] and my siblings are [name]Sarah[/name] and [name]Benjamin[/name]. We are [name]Lauren[/name], [name]Sarah[/name], and [name]Ben[/name].
I also know of these families:
MIX OF NICKNAMES AND NOT
- [name]Helen[/name] and [name]Olivia[/name], called [name]Helen[/name] and [name]Liv[/name] or [name]Livvy[/name]
- [name]Kathryn[/name] and [name]Jonathan[/name], called [name]Kate[/name] and [name]Jonathan[/name]
- [name]Rebecca[/name], [name]Hannah[/name], [name]Genevieve[/name], and [name]Madeline[/name], called [name]Becca[/name] or [name]Becky[/name], [name]Hannah[/name], [name]Genni[/name], and [name]Maddie[/name]
- [name]Angela[/name], [name]Amy[/name], and [name]Curtis[/name], called [name]Angie[/name], [name]Amy[/name], and [name]Curtis[/name] or [name]Curt[/name]
- [name]Melissa[/name], [name]Kimberly[/name], and [name]Jenna[/name], called [name]Melissa[/name], [name]Kim[/name], and [name]Jenna[/name]
ALL NICKNAMES
- [name]Maximilian[/name] and [name]Anna[/name], called [name]Max[/name] and [name]Annie[/name]
ALL GIVEN NAMES
- [name]Catherine[/name] and [name]John[/name], called [name]Catherine[/name] and [name]John[/name]
- [name]Caleb[/name], [name]Eli[/name], and [name]Jonah[/name], called [name]Caleb[/name], [name]Eli[/name], and [name]Jonah[/name]
As you can see, in my experience, families tend to overwhelmingly favor a mix of full names and nicknames. Whatever you choose for yourself, you are in good company!
I prefer longer names for both boys and girls so they have options for when they older but can have a nickname or more than one aswell.
I am the same as you - i have to have names that are shorten-able. This was the main criteria for naming our twin boys - that and having 2 different sounding names! Now we have done this, we want to keep on the same pattern.
I do, however, take it a little further than the ‘formal-name-with-nn’ rule and will not allow repeat of initial or sound - i.e. my boys are [name]Oscar[/name] and [name]Fintan[/name] ([name]Oz[/name]/[name]Ozzy[/name] and [name]Finn[/name]) I love [name]Sullivan[/name] - ends with an ‘n’ sound same as [name]Fintan[/name]; [name]Jasper[/name] - ends in an ‘er’ sound like [name]Oscar[/name]; and [name]Florence[/name] and [name]Otis[/name] - but already have those initials used - so all off the list!!
This is just my preference, but it sounds like you are similar so i say go with it. You’ll find names that go together that you love! x
I am much the same as you. I generally prefer longer names with nn potential for firsts, and good nns are very important to DH and I. Our children are [name]Ambrosia[/name], [name]Jasper[/name] and [name]Raphael[/name], whom we call [name]Rosie[/name], [name]Jasper[/name] and [name]Raffy[/name]. Because [name]Jasper[/name] is as short and easy to say as [name]Rosie[/name] and [name]Raffy[/name], I don’t think it stands out too much (we sometimes call him [name]Jazzy[/name], but [name]Rosie[/name] and [name]Raffy[/name] are virtually always called by their nns).
I’m definitely the same. My favourite girls names are usually 3 syllables but most of my boy favourites are shorter, it’s weird but doesn’t bother me too much. Also, I think when you have a kid their nicknames come naturally and usually out of nowhere so they’ll get one from somewhere regardless of how short their actual name is.