Knight training is a brilliant party activity. You tell all the kids they are going to learn to be knights and then take them through lots of training exercises. You can give out prizes for effort, elegance, accuracy and making everyone laugh!
My son had a brilliant time in a knight training session at a renaissance fair. They built all the kids up about learning all the skills that a knight needs - with wooden swords tantalisingly on display.
And then they told them that the first activity was learning to dance like a knight for when you had to entertain the ladies. It was hilarious!
They did teach the kids lots of poses with swords afterwards though.
Only let kids have foam swords as part of an organised activity - a free for all is not a good idea except maybe at the end of the party.
Add in some fun facts about knights. The Genuine and Most Authentic guide is a great source of knight facts for kids and makes a great gift.