You can still go and have a great time.
Personally, I hate having to plan so far in advance. I plan as little as possible as far as ADR's. I only get them for a few places that my niece wants to go and that are must go to places, etc. I just don't want to vacation around my reservations the whole time and keep looking at my watch! And I love to eat!
Keep trying and you'll find a Chef Mickey's, or almost any other place, for your trip eventually. It might be the ideal time or date, but you'll get it. I think Crystal Palace is the one with Pooh and friends though.
You still have time for FP+ and, unfortunately, there is no way around planning that!