Infected,
Great question and I think I can help you as well. Robert covered most of it. Forget doing card tricks unless it is just one or two REALLY cool things that involves some humor. Kids could care less at that age nor will they pay much attention. You want anything that is colorful, vanishing, reappearing, funny, flashy / fire, silks, money, rope, etc. You need to get them INVOLVED. Kids like to DO THINGS rather than just sit and watch. You need to be able to make fun of yourself as well. You ever watch Silly Billy perform? Hilarious comedy and kids eat that stuff up.
Here are a list of some things I use in my kids show: Stratosphere, Change Bag Routine, Lota Vase, Fiber Optics with Rope, D'Lites, Shoot a card with cap pistol, Spongeballs, and a ton more.
Do you need to go buy expensive props to carry around....if you are building a professional show...yes...eventually. If you are just entertaining kids for free then I suggest what Robert said, maybe get some cheap colorful silks, rope, coins, TT and go that route. Let me know if you have more specific questions on certain effects and I can tell you if they play well or not for 8-9 year olds.
Reality One is a very knowledgeable guy as well on kids stuff. Craig Browning knows his material well too but I am not sure if he does or did at one time kids shows. I'll let these guys chime in if they choose.