Start off nice and slow and easy. If it’s cocktail music, some jazzy stuff, Al Green, or even 40s standards, Sinatra, or Elvis works wonder(unless your mom’s family is very hip—remember, you’ll likely have a very diverse audience). Volume should be loud enough to sound good, but not so loud it inhibits conversation. Walk around and check it out.
You want the music to be energetic but not overbearing. Again, unless your Aunt’s guests are all pretty sophisticated EDM fans, save the house set for the end. You’re warming up, really, so your job isn’t to pack the dance floor. It’s to make everyone feel welcome and boost the general vibe. You can always work your way up in vibe/bpm (and you should), but if you start out too fast too early you’ll alienate your audience. Watch the crowd. Get the old folks tapping their toes—a lot of DJs neglect that audience, but it’s critical and often ups your tips.
And as Drew and others have suggested, just relax and have fun. The crowd is primed to dance, they’re drunk and forgiving, and unless you completely botch everything, the night will be successful and you’ll learn invaluable lessons. Play songs you like, but also remember that your job is to please as many people as possible. Smile and be part of the fun.
Good luck!
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