Hi, Ivette! You've got a great plan going with a 2 p.m. arrival and a 6:45 p.m. reservation at Chef Mickey's at The Contemporary. If you plan on taking your rental car from Coronado Springs, you'll need to plan on a 20-30 minute commute from your resort room to the restaurant. If you're planning on taking Disney bus transportation, you'll need to take a bus to the Magic Kingdom (MK) and then walk over to The Contemporary -- which may take 45-60 minutes from start to finish.
When you check in at Chef Mickey's, you probably won't be seated until closer to 7 p.m. The restaurant is a buffet. Therefore, it won't take long to serve yourself and eat, but you should probably plan on finishing before 8 p.m. (The characters come to all the tables.)
On January 5, Wishes Nighttime Spectacular (MK fireworks) begins at 8 p.m. Therefore, you'll want to find your way out onto the patio just on the other side of the Concourse of The Contemporary to see the show. (The soundtrack for Wishes is piped into the resort so that you can hear what park guests hear during the show.)
After the fireworks, you can shop there on the Concourse of The Contemporary, and then take the escalator up to take the monorail around to the other resorts -- The Polynesian and The Grand Floridian. You can check out the dining and shopping available there, too.
You can watch the outdoor movie usually set up in the area between The Contemporary and Bay Lake Tower or take a
specialty cruise from The Contemporary after the fireworks. You may want to take a boat taxi over to the Wilderness Lodge or to Fort Wilderness. At the Fort, you can take a nighttime carriage ride or check out Chip n' Dale's Campfire Sing-A-Long and outdoor movie.
Let me know if you need more suggestions. Have a wonderful day and a magical vacation!