Entertainment/games appropriate for a group of kids aged 2.5 to 11

[ohwhattodo1]

I'm organising a group get-together, and there will be children there aged 2.5 up to 11. They will have access to an outdoor play area, but I wanted to provide some games incase of bad weather.

Any ideas for a few games that would be suitable for all those ages? I can do pass-the-parcel but am stumped for a suitable prize!

How many children will there be in the different age groups? You could probably get away with a pass the parcel prize for 2-6 year olds (playdough maybe?) and then one for the older ones (an art/craft set or a bundle of sweets maybe?)