wow, is your trip in February? You might not get any ADR for Coral Reef...I just called for ADRs for the 3rd week of January and Coral Reef was not available for any time during the entire week they're going to be there. Was able to get every other 1st choice, but Coral Reef was booked the whole week.
As far as times go, if you're going to Epcot during a "down time" then I'd suggest no later than 6:00...if they seat you within 15 minutes of that, and it takes the average 75 minutes, you'd be getting out of the restaurant around 7:30. Take you 10-20 minutes to walk to a decent spot (if it's a light attendance week you can still find excellent viewing spots just 10-15 minutes ahead of Illuminations.)
However, if you're going during Presidents Day week, I'd go for no later than 5:30 reservation...you would want to be looking for a good spot by 7:15 if not earlier.
that's excellent...Way to go! You shouldn't have a problem with finding a good space to view Illuminations. That week should be relatively lower crowds...kids back in school after holiday break, but before winter breaks and 3 day weekends.
We will be there the week of President's day. Should be a little busier than your week, but not too bad judging from how easy it was to get other reservations...and how many rooms are still available, even on the 4/3 deal.