25 Adult Birthday Party Ideas [30th, 40th, 50th, 60th] | The best adult birthday party ideas for a 30th, 40th, 50th, and 60th birthday. This year I hope you throw an amazing birthday party for your grown up bestie, your man, or yourself. There are lots of adult party themes that can make your next celebration a blast! Find fun theme ideas and party planning tips for you and your friends. Party Themes For Adults ” ( total) Find great ideas for adult theme parties and adult birthday party supplies. Sort Results By.