be honest, do not ask in public, buy a bunch of "orange gerber dasies", walk up to her with them in your hand & hand them to her. then say something like "we've known each other for many years...i know i'm a bit of a goof but i really like you...would you let me take you to dinner"
i suggest gerber daisies because they are fun & set you apart. they make romance out of your perhaps slight immaturity (by the way, finding "dooty" funny is not immature...but maybe learn to grin & not laugh...i'm 50 & very mature & think "dooty" is still funny.