At the very top, I would change it so it says, "Create an account or sign in"
Labels are pretty standard here, so that's good. If you want to keep it clean, consider removing the labels and making the values of the text fields the label names. The values in the text fields are already pretty redundant.
Change the label of "Register!" to "Create account"
Error messages: could use some tweaking for the language. Depending on your tone and voice of your brand, you could make these more or less fun. You know kiters better than I do, but they seem like they are chill and may get a kick out of non-standard error messages.
You don't have a link back to the sign in page. Not everyone will get to this page from the home page, so you should provide them a way to get to that page.
the flow of the site will be an either/or, not a flow from the sign in page.. them main page will include [register or sign in]
Register page URL: /register
You don't have a link back to the sign in page. Not everyone will get to this page from the home page, so you should provide them a way to get to that page.the flow of the site will be an either/or, not a flow from the sign in page.. them main page will include [register or sign in]