I love little girl clothes too. There are just more options. Not necessarily pink and glittery, but little smocked sundresses or peasant tops. They make my heart melt. I have found that it's possible to find fun options for boys too. I stick to stripes, primary colors, or cute button-ups. In the winter it's especially fun because I can layer him in cardigans and sweaters. I know one day he'll have his own style and maybe he'll hate my twee outfits, but for now I love dressing him. He has some pink clothes too! They're designed for boys -- I think pink tones for boys are trendy right now.
With this baby, we'll have so many toys around from my son that I assume he/she will end up playing with them. I really agree that if a kid expresses interest in a toy, he/she deserves to play with that toy, no matter what gender it's aimed at! I grew up with brothers and we all played with each other's toys. If it's fun, it's fun.
I haven't really talked to my family members about it yet because it's just been a few comments here and there. If they persist, I'll probably gently remind them that the baby could be a boy and that we'll need to be ready to welcome him. I hope that when the baby gets here, the excitement will make help them just celebrate with us.