You will get charged for attending the meal. Mid October is a good time to visit, the weather is nice, the crowds aren't huge.
I have a son with Asperger's Syndrome, and after our last trip, we learned to travel in the off season and while school is in session.
He's also a fairly picky eater, and will get into a rut with food choices.
That being said, you may be better off with a character meal that serves a buffet where he's sure to find something he likes. We've eaten at most of the character meals now (I checked the list and we've missed the ones at the swan and dolphin and the princess ones...that's it

). Chef Mickey's is probably my boys' favorite, closely followed by The Garden Grill.
If you'd like me to get you a listing of what's served on the various menus, just PM me and I'll send it along. We keep it handy, as my son has some food dye allergies that exacerbate some of the AS behaviors.
If you find nothing on the menu that he likes, sometimes calling WDW dining (407) WDW-DINE is a big help. You can explain your issue (food dye allergy, diabetic, only eats whatever, lactose intolerant) and the chef will work with you.
Good luck planning your trip. There are several people on here with kids on the spectrum that can give you some advice and assistance!
Suzanne