We opted against doing that because even if you got in right at 5:00 and allowed for one hour for dinner (although I think we were there longer last time), you need to account for travel time and getting into the park, which may be difficult if lots of people are arriving specifically for Spectro/Wishes (which is possible because I know Spectro is only showing twice during our dates and we are hopping just for that). Then getting up Main Street for a seat.
We decided that we wouldn't be able to enjoy dinner if we were worried about getting somewhere on time (especially since my dh is one that likes to be crazy early for things!)
Hope this helps!