We tried the minimal people, cheap as possible thing last year. We ended up with 20 people with only 4 groups of people, bringing thier significant other and children. () we asked each family to bring a plate and had it in a park. So it didn't cost a lot. Maybe 50 all up with the cake.
We're not in any better financial this year. I'd love to take him to the zoo or aquarium but we just cant afford it.