This is an example of a Big Time Festival. When doing one of these, you really want to have all your crafts ready and have a good supply.
One of the crafts that we make are Marshemellow Shooters. These are very popular with the younger generation, they are hand made (so they meet the requirements of 'handcrafted only'), they are inexpensive to make and easy to transport. Each point is important. If what you make is not popular, it won't sell. If you buy it to resell, it will not be allowed in some shows and if it is difficult to transport, the cost may make it unlikely that you will profit from it.
One other point is .. You always want to have enough supply so that you don't run out. There is nothing more frustrating than being discovered by the public, getting really busy and then running out of stock. Everything comes to a grinding halt, including your sales and profit. If you are out of stock, you are out of business. Over time you will get a feel for how much of any certain craft to take with you, though there is always the chance that what sold last year at this festival may not sell this year. That is the nature of the business. Just make sure you have an abundance of everything. If you find that you are swamped with too much stock, take inventory after each outing and guage what is selling the best. You will probably come down to only a few crafts. Then you can concentrate on these and still have room for a little experimentation to fill out your offerings. Always have something new for your returning customers. They want fresh, exciting items. They really like to buy from you, give them the chance.
You can never have something for everyone, but you can offer the very best of what you do have. Remember, the Big Time Festivals are just like the small shows, just bigger. You will be fine!