It is never too late to make an ADR. I've walked up to restaurants without and ADR and been told no available seating. I then call WDW-Dine a few feet away with my cell phone, and about half of the time I can get a seating time within a 1/2 hour, .
The person at the podium is usually very surprised when I walk up and give my name and my ADR # and then they very happily seat me.
If the restaurant is truly booked up, I can usually get a seating time at an acceptable place in the time it takes us to walk or transport over
Carol