I prefer Roslynn or Roselynn (Rosalynn doesn't flow of the tongue with that much ease), but its okay. Personally, I don't think it honours the tradition your family has started. Usually I think any form of a name honours as long as you chose it with that purpose (for example a name I toy with quite often is
Annelise,
Anne for my
Nana and
Elise for me). However, in this case I think continuing the tradition is better and
Charlotte Rosalynn doesn't have any better flow than
Charlotte Lynn IMO.