If you officially extend your party beforehand by 30 minutes (i.e., your guests show up at 8pm), I can see how the planner would either charge you for 30 extra minutes of food or cut off food service after one hour (i.e., 9pm).
But if you start the party officially at 8:30, you and DH can show up 30 minutes early by yourselves and you'll still have food service til 9:30 (because when you two arrive, the server will still be setting up your food and food service will not offically have started).
Then, if you want to extend the party by 30 minutes afterward but don't want to pay extra for food service, the food will stop at 9:30 and guests can linger til 10. I guarantee you they will have had plenty of time to eat before the food service stops. My *guess* is that the server will begin taking down his/her setup at 9:30, even though you'll still be there, but when our server did this, he also let my MIL take all the leftover desserts.... perhaps this would solve your "what to eat after 9:30" problem...
I'm not sure what time IllumiNations ends, but it felt like we hung out there for a while afterward til the bus was ready and someone came to get the guests. I'm sure it wasn't 9:30 sharp, though. Maybe 10 or 20 minutes after? They seem a lot more casual about all these times when you're actually there than they are when you're planning (and paying!).