if you do team games with a mixture of games ie egg and spoon race, obstacle race, everyone takes turns the older ones help the younger ones. Pass the parcel to save on paper hot potato, parcel is wrapped once when it lands on someone when the music stops they are out they come for the token sweet who is left wins, sleeping lions is always great for calming a manic party down. If you have a twister board make each corner a colour, play music when it stops they run to a corner spin the wheel whatever colour it lands on they are out. You could always make a papae mache pinata.
Children do love a treasure hunt. I did one for my girls when the youngest was 4. She needed a little help with the reading but loved it. Since then I do one every year from Father Christmas so the girls have to find their presents on Christmas morning before they can open them, it goes down a treat. Over the last couple of years I've used www.tracetheplace.co.uk and created my own treasure hunt. You get to choose from a great list of clues which you can change if you want to and they're in catagories so you can pick for the age of your hunters. I found it a lot easier to pick from a list rather than having to think up loads of clues myself. You could even use it at the end of the party so the child has to find their party bag. If all the bags are the same just get each child to pick out a clue from a bag then go off hunting. If not, you can change the wording of the clues when you order so each child knows which is their clue. Considering what you get, it's really good value. From what I've said, it may sound complicated but it's really not