Linda, Do you already have a reservation with Dollar? If you do, call them now and add your fast lane number to it. If I remember correctly, this needs to be done at least 24 hours in advance.
As long as you have the fast lane number, it shouldn't be a problem. If you are doing this in the evening, don't call the special fast lane number. They are only open until 5pm. Just call the regular Dollar number.
Good Luck!
CC