You can definitely make lots of games on your own and not spend lots of money. Pinterest is a great source as you mentioned. You can even do a search on "inexpensive carnival games" and get lots of ideas!
As far as prizes are concerned, I wouldn't worry too much. Kids often like the idea idea and process of winning and getting a prize as much or more than the actual prize. Having said that, you could try asking for donations (perhaps from area businesses) so you can a little more. Also, you could try offering some grand prizes or special prizes like "lunch with the principal."
We're a K-6 school. Last year we had a police officer come to the carnival and he played ball hockey with the older kids, they LOVED it way more than the games. I think this year we'll keep the games pretty simple for the younger kids and invite our community officer again.
Each spring our PTO hosts a Fun Fair (like a carnival). It is one of our major fundraisers usually.
Normally, we hire a company that brings games and inflatables. We have been using the same vendor for years and the kids (and the parents!) are getting bored with his games. Some members of this year's PTO are looking into making our own games instead! I've been looking on Pinterest and there are LOTS of ideas! Other PTO members are afraid that making our own games will be too costly. Does anyone have thoughts on this?
Also, our PTO is low on cash this year and the Executive Board has asked the Fun Fair committee to come up with new ideas for the prizes. Normally, kids play games and earn "monopoly money", which they then take to the prize redemption room to buy prizes. In the past, the PTO has purchased prizes from Oriental Trading company and things have broken before the kids even left the school! And there's always a line for prize redemption. Does anyone have alternatives to this type of prize system?
We are a K-5 school, but the event is open to the community and the families of our students so ages of kids vary.