Amy - there is no such thing as a dumb question!!! I realize the pain and agony involved in planning and making ADRs, it just doesn't seem like vacation! But to answer your question quite simply, you only need to make ADRs for the restaurants you want to eat at.
My experience, regardless of time of year you go, if you plan to eat lunch at lunch, and dinner at dinner, make ADRs. You don't have to make them all, there's no penalty for skipping. But the fact of the matter is, with the amount of people you see on this board and other planning sites, you can surely bet that about 90% of them will be making ADRs. I wouldn't chance it, if there's a place you really want to eat at.
On a side note, as the previous poster said, there is NOTHING wrong with counter service, if you can't get walk up table service. The quality and variety is excellent. I would just not plan on going on the fly and getting your choice of Table Service.