I agree w/pp. Keep checking - especially as that 45 day mark approaches.
If you have children, I, personally, wouldn't try a walk up unless you are staying at the Contemporary. Otherwise you will travel there, be able to see into the restaurant and probably some of the characters and may not be able to eat there at all.
When we were at WDW with my kids, we did one meal w/o an ADR in Epcot - I walked up tp see if there was availability while dh had the kids busy with something else. When they said there was availability, he just brought to kids in. If there hadn't been availability, the kids wouldn't have even known I had checked and we just would have eaten somewhere else. Chef Mickey's is out of the way and, with kids, IMO, I wouldn't chance it.
Have a great trip!!