Get-It-Done Guy tackles the difficult problem of managing people older than you.
I take my cue from my favorite 1980s comedy, Working Girl, with Melanie Griffith, Harrison Ford, and Sigourney Weaver. When Melanie Griffith starts working for her slightly younger boss, Sigourney Weaver, Weaver does a quick check-in with Griffith to make sure age isn't an issue. Of course, Weaver also steals her ideas, stabs her in the back, and breaks multiple bones skiing, so be careful how much deep management insight you take from the film.
Don't Prove Yourself ... to be Young.
Once you've acknowledged you're young, it can be tempting to try to “prove yourself” by showing them you're an expert. Be careful with that. You're young. You're a manager. They have more experience and may be the experts at their jobs. If you do show you're better, you're rubbing their faces in the fact that someone younger is better. That's a great way to make friends. If you try to show you're better and you don't, you're confirming their suspicions that you're an ignorant puppy just waiting to be house trained.
As a manager, your job is to get things done, through other people. You don't have to be the expert in how to do stuff, you have to be the expert in how to help them get it done. Your job is team-building, helping people tap their motivation (which often just means getting out of their way), and making sure everyone has the same understanding of the goals and strategies for getting the work done. Then when the team is humming smoothly, when they hit a snag, they get to keep working while you run around like a chicken with your head cut off to fix whatever's holding them back. It does not look dignified to run around like a chicken with your head cut off—that's why your current boss always has those beads of sweat dripping from her mustache—but it is what 21st century career advancement is all about.