River? Please, no. Names associated with film stars (River Phoenix) are sooooo naff!
Maverick has a wonderful meaning (according to the Concise Oxford Dictionary): "Unorthodox or independent-minded person". It sounds a bit like you! However, I favour one or two-syllable names. (Your son would just get called 'Mav' anyway).
Scarlett? We're back to film stars again. (Scarlett O'Hara). Also, it would lead to loads of school jokes about a 'scarlet woman'.
Autumn? If you live in New England the word will conjure up images of beauty. However, if you live in Grimsby it will probably conjure up a picture of grey gloom!
From your list, I'd favour Hayden for a boy. It's a beautiful name and also the surname of one of the world's greatest cricketers (who announced his retirement this week).
For a girl, I'd favour Talia. However, the most beautiful girl's name I've come across recently has to be the traditional (but still fairly rare) Irish name, Fionnualagh.
Chris
(Well, at least one of us took your post seriously!