L.V.
Hi K. - I find planning kids parties a lot of fun, but often overwhelming when you start. I have found the best format for me is to start with some coloring pages or similar activity (that can be easily interrupted and finished at a differnt time) to keep kids busy until everyone arrives. Then use a story line to keep kids together - I've used a Blue's Clues format, a letter from Cinderella with clues that lead them to find the next activity, and even a Dora map to lead them to the cake...
I have found a ton of activity ideas at http://www.birthdaypartyideas.com it is arranged by type of party and age group. I have been picking and choosing from a lot of those party ideas to create one that fits my daughters' idea of fun (and the size of my house and budget).
Have Fun!