Welcome to the Moms Panel Alison! Love your name ;-D
The Crystal Palace is still an awesome place to dine. Character dining locations are very popular and reservations are recommended. They don't "hold" spots for guests without reservations. However, if there is availability they will do their best to accommodate guests without reservations.
If you know the date that you'll be visiting the Magic Kingdom, I'd recommend going ahead and
booking online or calling 407-WDW-DINE. If you don't know the exact day or are unable to get reservations, you can try walking up and checking availability. You may have better success if you check as lunch or dinner is starting. That way if you a larger time frame to try to get in.
If your family consists of little ones who may be disappointed if they don't get it, I'd send an adult ahead to scout it out. Your chances may also increase if you are traveling during a non-peak season.
Wishing you minnie magical memories :-) Allison