Omnisexual is a specific way of explaining your attraction, as bi can mean anything, from being attracted to two genders or more, to just being attracted to two.
If what you're trying to imply here is that there's only two genders, I'm willing to have a discussion with you about why you're wrong.
And no, bisexual does not exclusively mean the attraction to boys and girls, it just means attraction to two or more genders.