I think birthdays are one time of the year where it's okay to act like a kid again.  So yes, definitely balloons!  I think most of us would agree that once you pass 21, birthdays are not as exciting as they used to be.  

But, I don't think it needs to be that way!  As a party planner, you want to do your best to make the guest of honor have fun, feel young, and simply have a blast.

The silver/chrome accent idea is fantastic.  Definitely try to find someone with a motorcycle to give rides to the guests.  Have plenty of drinks to go around and casual, everyday party foods.  Fun outdoor games like corn-hole, horseshoes, and darts will be entertaining and will promote friendly competition.  

Basically, just try to think of what was fun for you and your friends to do when you were a young 20-something.  Help your guest re-capture his youth!    

Nice idea - tlatrice!

Colorful balloons I love them! Do you know any thing about cornhole game? I think you should plan that also!