Charles isn't my cup of tea. I think it is still a bit dated without a younger sounding nickname to liven it up. It also seems a bit boring and definitely upperclass to me. It's definitely possible to avoid the nickname
Charlie. There are other nickname options.
Charles HephaestusCharles HyperionCharles XerxesCharles DominicCharles UlyssesCharles FranklinCharles BartholomewCharles SolomonCharles QuentinCharles Bertram
Like any?