Congratulations on your upcoming party! I run a DJ entertainment company so my opinion on the music will be biased, but DEFINITELY get a playlist together of whatever type of music you and your friends want to hear before the party. If you have the budget, hands-down get a DJ, otherwise, if you already have some speakers, plugging in an iPod with the playlist already made should be great.
Look into maybe getting a tent for where you want the speakers and dancefloor. It'll help designate a good spot to dance. Put the food close - but not too close - to the dancefloor.
As for activities, you'll want to do things that keep people on the dancefloor. Cha Cha Slide, Crank That, and other dances will be a hit.
If you need any more help or advice, you know how to get in touch.
My company's website, www.PremiumDJ.com has some great sweet 16 party planning materials that you can use.