I just had a birthday party for Wesley about two weeks ago.
I ordered a doggie cake from a dog bakery, set out bowls with dog treats, and decorated my house with doggie decorations. Eight dogs came over and they all had a blast playing. I also had food for the humans. Then I sent everyone home with goddie bags.
I think the most important thing is to invite dogs that your dog already gets along and of course, treats are great too!
Please tell us how everything goes. Just have fun with it!