Hi Kay,
I have enjoyed both of the character meals that you are considering, and this is going to be a tough decision. Let me help you think through the possibilities, but do know that I think that both are great experiences!
Chef Mickey's is an iconic character meal. Here you will meet Mickey Mouse and his friends dressed in their chef gear, while in the amazing atmosphere of Disney's Contemporary Resort Grand Concourse, with the monorail whooshing by overhead. At
Crystal Palace, you will enjoy a great meal in a lovely Victorian building in the Magic Kingdom while being visited by Winnie the Pooh and his friends from the Hundred-Acre Wood. Please do note that all character appearances are subject to change.
The first consideration I would make is which characters your grandchildren are most interested in meeting. Character meals are a great way to meet and interact with characters, so if there is a set of characters that your little ones find more intriguing, that would be a start for your decision. Also consider timing. Most small children are up fairly early, so the early time at Chef Mickey's could be fine; however, remember that you would need to leave ample travel time if coming from another resort than Disney's Contemporary Resort, which could mean a pretty early morning.
All things considered, I would choose Crystal Palace. I suggest that you get to Magic Kingdom early that morning, schedule your
Disney FastPass+ selections for first thing, and then enjoy your midday meal at Crystal Palace. But remember - there is no wrong answer here!
I hope that these thoughts are helpful for you, Kay! Please let us know if you have any further questions.