I have 2 books that you may be able to find at your local library. We did a bowling alley party this year and it was expensive so next year I?m planning to have the kids pick out something from the books.
Birthday Parties for Children, How to Give Them, How to Survive Them by Jean Marzollo
The Penny Whistle Party Planner by Meredith Brokaw
I liked the penny whistle one best. When I looked it up on Amazon (to double check the title) there were a few others also written by her. Also, you said you had a source for papergoods. Another place to look is on your local Freecycle list. I have seen many offers of party invites, etc.