should I ask my boyfriend to prom?

okay so I've been dating the same guy for 4 years. he's 20 & I'm 18 I'm a senior in high school and when he was a senior I went to his prom as a freshman. I really want him to go to my senior prom since he didn't go to my junior prom. I don't want to seem childish & him be like no because he's to old for high school stuff, but I really want him to go. I also wanted to ask him in like a cute corny way but I just don't want to come off to childish but we also have a close relationship so maybe I'm over thinking it... help 😩