Twin Names, both genders

We are having twins but I can't decide on names at all. 
We have a toddler named Lucas Cotton. We call him Cotton. 
I love a names that aren't names. Like plants, but I also like Arrow. I like a combination of a good, strong first name and a fun "word" for the middle name. 
I think I'm overwhelmed because I have to pick two and I don't know what the genders are yet. Help please!