Dr. Susan has some good advice on how to eat well. This is always a critical component of a good exercise plan. Eat well, sleep well, and the body will be appropriately fueled for the exercise effort. There are no short cuts to success.
But you knew that!
That is part of the reason why you have picked out a good run for next Thursday. An official race is good even if you don't "race" it, you get timed mile marks, water stops, and emergency medical support for the length of the run you can handle.
If you don't go for a race, get a couple of buddies together. Company is always good on the run.
Worse case, get your own two feet out the door and moving.
The big dinner later will be a real reward for the effort you left on the roads that morning.
May the roads be kind to you!