My daughter wants to have a big party how can I make it not so much money?

What are some ways to make the party a low number of cash?
It’s her 13th party and she wants to have a big boy-girl dancing party. It will be in our backyard(which is big) and I already have speekers and the DJ booth so we would just have to buy the music. She wants it at night with lanterns everywhere. How many people would be good I’m thinking between 25 and 50. Any other ideas? Thanks I’m trying to make it not so expensive so I can buy her a nice gift without being broke.
I’m not spoiling her I never do this unless it’s special occasion and also shes been getting really good grades so I want to reward her. (straight A’s and is in advanced classes)
Instead of gifts she’s asing for donations to a charity, any ideas on what one.
Whats a good amount of money?
She can’t decide on the color theme what would work, maybe 2 colors?
She wants to buy lanterns from here http://www.lunabazaar.com/index.asp?PageAction=Custom&ID=9
which two colors would work?

I like the pink green and orange colors together for the lanterns. string them up along some Christmas lights that are hung up all over the yard- borrow extra strings from family memebers if you need more- will look like stars in the sky at night and be very pretty- that way you can cut down on the number of paper lanterns also. I think i saw some of those lanters at the Dollar store- check there first before ordering and paying for shipping also. for the music put your daughter in charge of that- have her burn CDs of all her favorite songs or hook up an ipod and just put it on shuffle so you have a mixed variety of songs. plan out a few fun games they can play as the party starts to get them loosened up a bit, heres a link to some fun games- have her pick out a few she thinks will be fun for the guests to play http://www.partygamecentral.com/pgcstandard/gameliststd.asp?type=teen&catname=TEEN+PARTY+GAMES. have regular snacks- chips, veggie tray, cookies, taco dip and maybe pick up some pizzas for later in the night (a place by me has these 24x36in pizzas for like $25, maybe you have someplace like that by you that will deliver to save you time, otherwise Little Cesars- if you have those- has $5 pizzas but pick up only) get it all form either a bulk store or Aldi has great deals on food- I always shop their for party supplies to cut down on cost. have 2 liters of soda instead of cans so they dont get wasted- have a marker handy by the cups so they can write their name on their cup. have a couple garbage cans out so hopefully most of the trash will make it in there on its own to save you clean up time. pick up some sparkelers for later at night that the kids can play around with.