I am a 20 mile a weeker, I normally do a 5k once month. I have one coming up on Saturday and then another on Thanksgiving morning. If you were me what mileage would you do between the Saturday race and the Thursday race? Wednesday is a rest day for sure but what about the other days?
For me that would depend on how you normally treat a run-up to race day. Are all your runs the same distance? Do you do interval/sprint work? How many days a week do you usually run?
I'll make a few assumptions and figure on running 5 days a week for 4 miles each at about the same speed. If you are not worried about making a personal best on the turkey trot then it's just a matter of not killing yourself on a quick turn-around race. You are not running Wednesday so that leaves three days. If it was me, I would not run Sunday to allow a day of recovery from hitting it hard on the Saturday race, then run both Mon and Tues. Monday would be nice and easy. Tuesday a bit more agressive but nothing to punishing.