It would definitely be weird to have
Hadley and
Harley together! They're far too similar. I suppose it could be OK if one is a middle name.
I don't like either
Hadley or
Harley. They're too trendy for me, and sound too unisex. I think they both sound more like boys names, but that's because I always tend to side with the boys when it comes to unisex names.
I'd much rather see a male
Harvey or
Harry than a female
Harley.