You can try, particularly if you get there at opening, but Chef Mickey's is busy, so don't be surprised if they tell you to come back or tell you that you will have to wait, possibly until your ADR time (and 2 hours is a long time to wait).
I probably won't try it myself just because I would have to make a special trip to CM and won't want to have to leave and come back if I couldn't get in. If it was a Restaurant in a park where it is easy to continue on touring if no, I would probably try it.
Some people have reported being seated early, but they were going to non-character restaurants in slower seasons.
Only time we really tried to be seated early was lunch at Sci-fi and it was about 30-45 minutes early (it was four years ago and I don't remember exactly how early we were - early for our ADR, but not enough time to really do another ride and get there on time) and we were not seated until our ADR time.