[Opinions] It's problematic but I do like it (m)
Charles Evelyn would be easier. Evelyn has pretty well crossed, similar to Vivian and Meredith. It's been used on girls for over 100 years. In saying that, I still see it occasionally as a middle name for boys in English BAs. Usually the 'upper-crust' announcements. I guess it depends where you are also. In the United States it is a hot girl name right now, much harder for a boy Evelyn and because so many people are unaware it was a male name too, I'm sure it will cause much confusion.
I don't subscribe to the idea that giving a boy a 'crossed' name is doing him a disservice but some work better than others. I think Evelyn is preferable to using Shirley for example but not by much.
I do dislike Evelyn on girls.
Evelyn Waugh's first name was Arthur. Because it was his father's name too and he hated his second middle name, he went by Evelyn "a whim of my mother's", despite not liking it.