Your crocs shouldn't be a problem for most rides at WDW. The only one where you will definitely need to remove them is Soarin', since they can slip off during your "flight." As previous posters indicated, you can leave them on the floor or put them in the basket underneath your chair. Tons of people have to do this, so you won't be alone. RnR does inversions, but as long as you keep you feet flat on the floor (not waving them along crazily), you should be golden.
When it comes to shoes at WDW just make sure that they are super comfy for long distances. I don't own crocs, but I have heard they are super comfy; HOWEVER, if you don't like them for super long distances, you might want to bring a different pair of shoes.