I have a similar situation.
Liana is our top name, and I don't think it's going to change. I definately want my first daughter's middle name to be after my ggrandma
Clara. But
Liana Clara doesn't flow all that well. I haven't decided whether to just use
Liana Clara or go with
Liana Clare, even though my ggrandma never went by
Clare.
If I were you, I'd tend towards
Charlotte Lynn because of the family connection. I'd also look around to see if there's a way to improve the flow though, if you wouldn't mind some tinkering. Maybe
Charlotte Belinda, or
Charlotte Rosalynn?
I prefer the
May spelling.