The rain will definitely keep crowds lower than predicted. We were there in mid December and one of our days if rained
All
Day
Long.
Torrential and heavy. Never a sprinkle. But, we were prepared. Rain jackets, zip lock bags, portable shoe dryer, extra shoes, socks, shirts and pants!
We were able to zip through the park quickly and get it all done. We went back to the resort, put on dry clothes then hit another park and zipped through that as well.
The next day, when the sun came out so did the crowds. We were able to take it easy.