Decorations: We planned a party that could be held outside or inside depending on the weather (we were lucky and good weather prevailed), so the decorations had to work either way. I opted not to have balloons, as they could get popped and the pieces are a choking hazard to our 18 month old. Instead I used plastic flags on strings (like a car dealership would use). Flags are more appropriate for a castle then balloons, anyway. We strung them from the trees and other outdoor structures. Inside they would have gone around and across the room. They worked really great for an outdoor party. We have a large backyard, and they flags made it look really festive without a ton of decorations. They went up in less than 5 minutes.  I bought pink roll paper from a teacher supply store for banners. It was thin enough to be perfect for door decorations if the party would be held inside. Just in case, I cut them door length, so they could be used that way. As it was, I hung them off our deck. I painted designs on them. On one I had a castle and a large number 5. On another I had a shield and crown and my daughter's name. After the party I added some pictures of the big day and they made wonderful decorations for the door to my daughter's room.  I had a lot of "little helpers" for the rest of the decorations. The centerpiece was a large box castle. It had a front door, and a crawl through tunnel that led into a large appliance box.  The children could walk through the front, crawl through the tunnel, and come out the back door. We hot glued boxes together (including smaller tower and turret boxes) with a hot glue gun. Then my husband painted it gray with some old gray house paint. I then gave my daughter, her best friend, and her younger brother paint pots and brushes and set them free. They made shield designs, extra windows and doors, and all sorts of doodles, designs, hand prints and blobs. I had mixed white into all their paints, so they had pastels. The colors looked really nice on the gray, and the whole effect was pretty, splatters and blobs and all! We cut out construction paper flags and shield designs. We used dowel rods to mount the flags on the turrets. I told the girls about shields and how they were divided and how the symbols told about the person and their family. I gave them a set of markers and the construction paper shields and they spent hours coloring and designing them.  On party day we pasted them on the castle and other places as great decorations.  I'd say the party preparations were as much fun as the party for my daughter!