Fruits bowl and vegetable bowl,candy and mix a variety candy together set the theme up with both the seven and eleven year olds favorite colors and use those colors for streamers,balloons,napkins and plates and spoons, partycity.com and walmart also target has great party stuff and you could get pizza,hamburger or barbecue, shrimp bowl and cookies and a cake u can get ice cream cakes from dairy queen,coldstone,walmart, tcby some good themes would be sleepover theme,camping theme,barbie theme,a fairies theme,a unicorn theme,a wizard of oz theme,spa party theme,fashion theme w/ fashion show,design clothes,spa,makeovers and alot u can do for that theme,amusement park theme,carnival or circus theme park ,water park theme,park theme,a safari theme,a candyland theme,A pool party theme,arcade theme, also good girl music with no cursing in it for a girls party would be getting girl group songs like the little mix band,fifth harmony,selena gomez,demi lovato,the staurdays,the electrics,the dream, for games board games,scavenger hunt,bouncy house,swimming pool,water slides,dance party games,video games like just dance,movies,talent show,spa time,fashion show,have them design cookies,make bracelets and jewelry kits,rose art crafts would be fun,coloring and painting pictures,contest and one more theme could be a zoo theme or disney princess theme and they could make ice cream sundaes too
It depends with your budget and the number of guests. If majority would be kids, there would be no need to serve food just soft snacks. You can make a dress up party for your daughters. You can get more ideas from http://www.thriftyfun.com/tf98305864.tip.html.
you can never go wrong with Hello Kitty, the smaller Sanrio products are pretty inexpensive ,and some you can buy in large amounts for the gift bags. You can get a Hello Kitty cake ( ice cream or regular cake). Hot dogs are always fast and easy. You can also have some sort of craft party, but some notebooks, and get different stickers ( the ones that look like jewels, or animals etc). Games are good too. My favorite one to do for my niece is called "pass the parcel" get a few trinkets and one larger gift (like a pack of markers, or costume jewelry) wrap the best gift and then keep making layers of wrapping, in some layers put a small trinket, and then add another layer, then you play music, and whenever the music stops, the person who is holding the parcel, unwraps a layer, until all the wrapping is gone. It's sort of a better version of musical chairs.