At Jack's party we had a huge age range of kids (lots of kids in the family)

For the under 2's we had...

A t-shirt with their names printed on them (made them myself with iron-on transfer paper)
A bottle of bubble mix (like they have at weddings..very cheap from $2 shops)
One of those fancy curly straws (very cheap from BigW)

You could also add a fruit stick, baby biscuits, baby muesli bars etc..