Well, for girls you know that my personal preference with [name]Ari[/name] and [name]Christopher[/name] is [name]Tessa[/name], but [name]Helena[/name] is a beautiful name, too - I really don’t think you can go wrong!
I suppose I have to address the issue of [name]Tessa[/name] Tolka … I like it. I think the alliterative nature of it makes it snappy and spunky, and so fun to say. Plus, [name]Tessa[/name] isn’t so popular that she’ll have to be called by first and last name all of the time, so it won’t matter much in everyday life, in my opinion. However, some people might not like the alliteration, and I just want to make sure that you do!
As for the popularity of [name]Rose[/name] in the middle, I actually think the issue is more or less negated when it is only one of two middle names. Its beauty can’t be denied, and with an unusual second middle like [name]Millay[/name] (I love the poetry connection) backing it up, its popularity doesn’t seem so obvious, or to matter so much. And I don’t think [name]Millay[/name] is too masculine; it does sound like a surname, but that sounds good in the middle. And it’s too close to [name]Milly[/name] to really be masculine.
If you’re not sure on [name]Rose[/name], seeing as you were enquiring about suggestions, other pretty one syllable names include [name]Blythe[/name], [name]Pearl[/name] and [name]Ruth[/name]. I think all would fit well with [name]Tessa[/name]/[name]Helena[/name] and [name]Millay[/name]. You could go with Rossetti instead of [name]Rose[/name], too, for a double poetry dose 
For the boys, I like that [name]Lucas[/name] has his own initial letter. It’s not a big deal and I’m just being fussy, but I like each child to have their own letter, especially as in this case [name]Ari[/name] would be the only one without a C name. That said, it’s not like you’ve given ten children C names and poor [name]Ari[/name] is the only one without one, and I hardly think he’ll be traumatised by it.
For middles, you might like [name]Rowe[/name] if you like [name]Rose[/name]. Are there any more admired figures that could be used as namesakes? Other good poet surnames include [name]Frost[/name] ([name]Robert[/name]), Marvell ([name]Andrew[/name], although it looks unfortunately like a yooneek spelling of ‘marvel’), [name]Barrett[/name] ([name]Elizabeth[/name] [name]Barrett[/name] Browning), Baudelaire ([name]Charles[/name]), [name]Byron[/name] ([name]Lord[/name] [name]George[/name]), [name]Eliot[/name] (T.S.) and [name]Hugo[/name] ([name]Victor[/name]).
Oh, and you could use [name]Vincent[/name] and still honour [name]Edna[/name] [name]St[/name]. [name]Vincent[/name] [name]Millay[/name]!
Good luck! [name]Auburn[/name]