I like [name_m]Theodore[/name_m] ([name_u]Baby[/name_u] [name_u]Teddy[/name_u]! Gah! So adorable!) and [name_m]Henry[/name_m] (a personal favorite) best, but [name_m]Franklin[/name_m] works well with your crew, as well. Fantastic options!
I think [name_m]Theodore[/name_m] would be a perfect name for #6! 
I think [name_m]Theodore[/name_m] would be perfect with your other children’s names, though I almost chose [name_m]Henry[/name_m] for you but thought [name_m]Theodore[/name_m] fitted in just that little bit more.
[name_m]John[/name_m] or [name_m]Jack[/name_m] for [name_u]Kennedy[/name_u]
[name_m]Wilson[/name_m] (as in [name_m]Woodrow[/name_m])
My favorites are
[name_m]Franklin[/name_m]… nn [name_m]Frank[/name_m]
[name_m]Lincoln[/name_m]… nn [name_m]Linc[/name_m]
Thanks, @care. I know too many little Lincolns right now, but I do love the idea of a little [name_u]Frankie[/name_u]/[name_m]Frank[/name_m] ([name_m]Franklin[/name_m]) running around.
@jh, I think [name_m]John[/name_m]/[name_m]Jack[/name_m] are very handsome but are too close to our [name_u]James[/name_u]. Same with [name_m]Wilson[/name_m], very nice but too close to our [name_m]William[/name_m]. I guess I’m kind of picky about the first initial not being shared by our kids (although DH and our oldest child share their first initial).
@adelina_sophia and @pippakate, I really like them both but [name_m]Theodore[/name_m] does fit just a little bit better.