Wants is the polite way. While wanna is slang.

Don't use the word "wanna." Don't. Don't. Don't. It is grating to hear someone intentionally say "wanna." It doesn't sound "natural" or "native." Native speakers say "want to" really fast and slur their words. They don't say "wanna." They especially do not write "wanna." Just don't do it.

Standard: Do you want to go to the park? Slang: Do you wanna go to the park? You wanna go to the park? Wanna go to the park? They all mean the same thing, but "wanna" is slang. You use wanna around people you are familiar with and in informal situations :)