If you are a paying, overnight guest at a resort, you are welcome to park there for as long as you want...and go wherever you want. If you pay to valet park, but are not a guest of the resort, you can leave your car and go wherever you wish.
If you are not a guest of that resort, but are eating/shopping there, you may self-park there while you are physically at that resort. You are then expected to move your car when you are leaving the resort.
Here's the thing.....it's actually no big deal to park at the TTC and then monorail to your ADRs. It's really not fair to those staying at the resort to have others park there, for the day, and leave and go to a park.
Now....can you get away with it? Probably. Do what you think is the right thing to do.