On our arrival day, we usually have dinner at a monorail resort, then go into the MK just to soak up the atmosphere and enjoy Spectro and Wishes. If we should happen to catch an attraction or two, great, but it is not our GOAL. Because we are not trying to get stuff done, we can enjoy a leisurely dinner outside the park. We used to do Chef Mickey when the kids were younger, but this trip we are looking forward to either 'Ohana or Kona (if we can't get 'Ohana).
In your case, since you are arriving late in the day, AND it is your goal to get lots done in the MK, I agree with the others who have suggested that you stay IN the MK for dinner. Even if you go to a restaurant on the monorail, you will spend AT LEAST an hour in travel time (walking to the monorail or boat, waiting for the monorail or boat, riding the monorail or boat, and then the same thing returning, and this is a busy time of day for the transportation system). Even walking to the Contemporary will cost you valuable time.
I would also avoid a place which requires a credit card guarantee (CRT), just incase you run into travel delays and cannot make it to your ADR. With these considerations, I would recommend either Crystal Palace (a buffet with pooh characters), or Tony's Town Square (sit-down Italian a la carte meal).
Hope this helps!