I know that Pecos Bill's is open until one hour prior to Eride ending and Casey's Corner is also open. The ice cream shop and bakery are also open. Cosmic Ray's may be open, but I'm not sure on that one.
We closed Pecos Bill's at 1:00AM last July 8th on E-ride night(11PM-2AM, so we actually ate on the 9th), even getting service with a smile. And a bunch of extra fries I might add. Some of our party went on Space Mountain after with no ill effects. Had a great evening in every way!!
They keep selected places open. They won't try and kill you! I got fries on mainstreet USA. Mainstreet USA is probably the place with the most food. So if you are making a switch from tomorrow land to frontierland, hit mainstreet usa and pick up something to eat.