My Daughter turned 5 and wanted a Harry Potter party.  I don't know if she had more fun or if I did.  First the invitations, I lucked out in getting them on clearance at target, but I also included an insert that I printed out on parchment paper on our printer. It said, "Welcome to Hogwarts! The Adventure begins at platform 9 3/4. (Alisha's house) You are invited to bring your Muggle parents for fun and games. Don't forget to dress in wizard attire, and make sure to bring your broom for flying races. (Broom parking will be located at the entrance to the platform.) There will also be a magical lunch served in the Great Hall. School term begins on April 12th promptly at 1:30. We await your RSVP by owl (or by Muggle phone.) Yours sincerely, Minerva McGonagal Deputy Headmistress.  And then I signed her name. I had the parents put it on their childs pillow and tell them that it was sent by owl post.  When they arrived I had a bin on the front porch that said broom parking. Every one came in and ate in the great hall and then we all lined up to go to Gringots bank.  My brother was the banker inside the closet under the stairs. He had fake gold galleons and asked each child thier password. After they had thier money, they went to Diagon Alley, where, my two sisters were dressed as wizards and the kids bought supplies for their classes. Quills made out of feathers with q-tips taped to the ends, wands (cinamon sticks), some plastic frogs and snakes in a glass jar with salad tongs to get them out with, and Harry potter glasses out of black pipe cleaners.  I found some gold material at the thrift store and cut out (no sewing)about 5 capes for those who didn't come dressed up they could buy one.  Then each child was given a ticket and we were off to Platform 9 3/4 (our front porch). My mother in law was the engineer with a train hat and red scarf around her neck. She punched each ticket and read them a train story book in her funny english accent.  Next it was on to the great hall where each was sorted by the sorting hat. I took a tape recorder before hand and recorded the sorting hat's voice from the movie. My sister and I made the sorting hat out of crumpled up brown paper bags.  Then they stayed at the table where they took out their quills and dipped them into lemon juice and made invisible messages, if you heat it up later on with a heat gun the message will appear, we actually just left it because of all the other activities we had planned. Next class was levitation where they put a raisin into a glass of sprite and waved thier wand "wingardium leviosa" the raisin is supposed to go up and down in the glass.  Then we went outside for flying lessons my other sister was Madame Hooch and told them to say "up" to their brooms, then we had flying races across the back yard. As they were out there, we brought out the pinata made to look like the golden snitch. The last activity was the search for the sorcerers stone.  I put some cool stones that are used in fish tanks inside of some plastic easter eggs and told them that the dragon, Norbert laid some eggs around the yard and they had to find the ones with the sorcerers stone inside. Then everyone came in for presents and cake. I made the cake like a Hogwarts castle with icecream cones for the towers.  It was fabulous and easy to do! One last minute idea I had before everyone arrived was to put a sign on everything, GRINGOTS BANK, DIAGON ALLEY, PLATFORM 9 3/4. We even have a decorator tree that I put a sign on saying BEWARE OF THE WHOMPING WILLOW. And having the soundtrack plaing in the background sets the magical mood (got that from the library.) I have to say it was a huge success and a great time for all, especially my daughter who will always remember her Harry Potter party!  Thank you to this great website and all the ideas of everyone who has written in!