Tinkerbell parties are very popular! Start with a set of Tinkerbell plates, cups and napkins, find a Tinkerbell cake top (or use a plastic Tinkerbell figure with fairy friends). You can also find Tinkerbell pinatas and mylar balloons.
Use Tinkerbell clip art (use Google Images to find pictures of Tinkerbell) to make your invitations or decorations. Maybe you could create "Pin the fairy on the tree" for an indoor game (like Pin the tail on the donkey).
Facepainting is always fun, kids love it! Do fairies or shooting stars (easy to do).
Finish the party off with Tinkerbell party bags filled with Tinkerbell pencils (from the Dollar store), stickers, erasers and maybe a coloring book (you could even make your own).