If you want to be totally assured that Eeyore will be there, you will NEED to go to the Crystal Palace.
Let it be said now, though that although I am a TOTAL Eeyore freak (can't you tell by my screen name?) that I would still choose 1900 Park Faire. The food there is WONDERFUL, the service is "Tiggerific" and the characters are great, no matter which ones happen to be there on what days. When we went, it was Mary, Bert, Alice, Pooh and Tigger. I was a bit disappointed, but soon got over it! After it we were done, we hopped on the monorail and I tracked down Eeyore in the MK to get my daily dose!