I'm a huge fan of not sending bags of plastic junk home to my friends houses for them to throw out!
I love party bags that are different.
Seeds or bulbs are a hit - if the party is soon give each kiddie a daffodil bulb that will sprout in spring.
Crayons/pencils
Mr men book
Fridge magnet
Little packet of tissues ( or a hankie for that matter)
Or a $2.00 scratchy (there could be a very happy party goer!)

Or I have seen really cute calico bags with a picture printed on them that become the present

Do a search for party favor on etsy or madeit and you will get heaps of ideas