I find that if you find a theme parties and the games associated are easier to organise. Think of a theme; some of the popular ones at the moment are Under the Sea, Pirates,Magic and Ben Ten (although this is a bit controversial as lots of parents don't like Ben Ten),then just google the theme with Under the sea party for example and you will find an area where people have put in complete lists of party games, cheap props made with cardboard, odds and ends and a bit of imagination and then there are lots of small places you can hire for not much money. I have approached local pre-schools and day care centres, scout halls and council playgroups. Often the deposit is high but the final price, once you get your deposit back is not too bad.
I am not sure where you live but the other option, if you only have a few children going and you are in Sydney there is a place called plaster Master where they organise birthday parties and the children get to paint a little plaster mould that they have selcted themselves. I am sure they will have similar type places all over Aust. It is expensive if you have a lot of children but it is quite fun and original if you just have a few.
I hope this gives you some ideas. If you have selected a theme I am happy to help you out.