I had a Barney-themed party for my son's 1 year birthday last year. I gave each child a brown paper bag to decorate with crayons and my homemade Barney stickers. They also had Barney, Baby Bop and BJ pages to color. The one thing I spent a little money on was a toddler-friendly Barney pinata, in which each child held a string and everyone pulled at the same time. They filled their homemade bags with the candy and prizes.
Dollar stores are also great for pinata fillers.
I have found a cheap, extremely inexpensive, and environmentally sound way to reduce the number of mosquitoes that invade our backyard outings. First, remove all standing water. If you have plants that you water often, make sure they have proper drainage. Buckets of water or other devices that hold water are great breading grounds for mosquitoes. Second, citronella plants are effective up to about 10 feet from the plant.