I think you should be fine going without a gender. Not everyone identifies with one. They works so you don't have to use it. Perhaps they are the combination of both genders or the absence of them. Just depends on how you want to write things. I might know a little about different gender Identities if you have any questions.

Nickname might help overall, or initials for the first draft and you can adjust the name later if you need to have it full in the final draft. This is going to be a rough draft so whatever way gets things done, go with that. At least we go by word count and not letter or character counts.