These rainbow streamers could be part of the decor and one of the activities. You could make them yourself or purchase them for $10 each at RosieHippo.com
Ballons are easy and fun and can leave your home immediately as part of the party favors. :)
I love the idea of having flowers at every party. These are just white daisies that have spent a few days in water with food coloring. You could make about every color in the rainbow. You just have to plan about 3 days ahead on this one.