The organized rides I've done around here typically offer bagels and peanut butter or cream cheese, bananas, apples, oranges, maybe cookies, water and some sort of "other water" - gatorade or other sports drinks. Sometimes they will have bars - Cliff, Luna, Kashi, whatever. Some rides feature pie and ice cream at rest stops.

As far as a "lunch" - if this is something served after the ride it could well be sandwiches, fried or BBQ chicken - and typical side dishes.

There will probably be some things you can eat at all the venues, but you may want to supplement with a couple things you bring - dried fruit? nuts? (I don't know what celiacs have to avoid so forgive me if I've made a faux pas). You could mix up some gorp or trail mix - about 1 oz each in little baggies and carry a couple baggies in your pockets easily.

Have you asked anyone who has done the ride in previous years to get an idea of what is provided?

Good luck.