。、。、。
Ta-da! All right, Haruta — you can look now. Time to unveil everyone's yukata~
Literal
Ta-da. So Haruta-[polite-くん], already look [even-ても] fine [feminine-わよ]. Everyone [gen-の] yukata, unveiling [emph-ねぇ]~.
ジャーン is a stylized mimetic for a dramatic reveal — the 'ta-da!' sound effect. ~てもいい 'it's okay if X' is the permission-giving pattern. くん is the familiar/diminutive suffix for boys and junior males. お披露目 (literally 'honorable exposing') 'public unveiling / first presentation' is a set noun for reveals — used for new outfits, new businesses, new babies. 浴衣 (summer cotton kimono) is worn at festivals and fireworks displays.