Well, I don't know if our party is going to be strictly "Waldorf' but, my daughter is turning 5 soon and we are a Waldorf family.
So what we are doing is...
A garden party. It's a 3 hour afternoon party in a local garden. I will ask parents to please bring picnic blankets as lunch will be a picnic which I will lay out on tables buffet style.
When the kids arrive they'll be given a clay pot to paint. When dry it will go into their goody bag with a packet of seeds. We'll do a bug hunt with the kids searching for bugs/fairies/gnomes that I will have hidden all around the garden. They will collect them in jars which will go home with them along with a little magnifying glass.
Other than the food, couple of games and maybe a big silk parachute to play with, I am looking into a story teller with a acoustic guitar who will play folk music during eating and tell a little story to wind up.
I am ordering little cotton bags for the pot and bug jar and will also include a bag of marbles and a packet of Tinti (http://www.myriadonline.co.uk/bath-time.php
) as well as a couple of sweets to take home. I found some beautiful all natural flower shaped lollipops.
Personally, I am not keen on competitive games for kids this age so I'm sticking with activities that stimulate imagination where everyone wins. I also don't think they need too much structure but I do like to have a quiet beginning (painting) and a quiet wind up (story).