I to did not know the gender of my fisrt baby ( girl), or my twins(girls). It was so much fun to be delivering twins and not knowing if it was 2 girls, 2 boys, or one of each. The only pain was having to pick out 2 boys and 2 girls names.
Anyway, I would think since the baby will be born in August, they will mostly be in onesies, so not to worry about gender specific clothing. And honestly it did matter which color clothing I had on my girls because people would still ask "are they boys or girls"?
Good luck with the new one.