Watch Wishes at Magic Kingdom first?
No, I don’t think this is doable. If this is during the winter months and Wishes is at 9:00, then you have a 20 minute fireworks show, battle the crowds to leave the park, then 15 minute monorail ride to Epcot (plus transfer time from MK express to Epcot loop at TTC), then walk to Coral Reef… the soonest you could possibly get there is 9:35, and if this is during the winter, then Epcot has probably already closed. And if you do get in, you’ll be at least 45 minutes late to your reservation.
Now- if you want to eat at Coral Reef first, then you’ll have say at the fastest a 45 minute dinner, assuming you got seated on time that would put you at 9:35 (definitely out if Wishes is at 9:00), then exit Epcot and take a 15 minute monorail ride to MK (don’t forget, you have to transfer monorails at TTC), that would put you at 9:50 at the absolute minimum time, not including walking time, monorail delays, lines to enter the park, or crowds.
One option - watch Wishes from TTC. They play the music, and you have a good view of the castle. Then, you can just hop on the monorail and head to Epcot or vice versa. But, you’re still at risk of not seeing the entire show or missing it completely.
If you’re dead set on seeing Wishes, I’d cancel the 8:50 Coral Reef ADR. However, if seeing Wishes would just be a “plus” and Coral Reef is the priority, then risk it.