I'm sure you will get lots of thoughts on this however I would never again use a
travel agent for free dining. We booked our reservation once (and only once) with a TA because we had a
DCL cruise booked with her and I thought it would be easier all around if she booked everything. In the mean time I booked three other rooms for family members who decided to go with us on the WDW portion of our trip. I sent her a message when I heard free dinning was coming out asking if she could make the for us. The morning it dropped I was able to change the bookings I had made with no issue however all I received from the TA was a form letter she sent to all her clients asking we not bother her, if she could make the change she would contact us and let us know. I didn't hear from heart all that day and it was stressful. I managed to get FD for all the others going with us but I did not know if I would get it.
Save your self the worry and just do it on your own. Again, JMO and I'm sure lots will have other thoughts. I just know what I learned from my one time experience and never again.