Don't change parks but be more flexible. My son's 20th birthday is Monday (he was born 6-6-96 we always joke about that) and his favorite park has always been AK. He gets very few days off work so we planned it all out, including fp for the new Jungle Book show. It looks like an all day rain event now so on Sunday night I will check the forecast and probably change the JB fp for Dinosaur.
We still plan to be there from the afternoon until closing and I'm sure the park will be less busy so we will be able to enjoy it that way. Maybe even go on Kali, it's my least favorite ride there cause you get wet but since we will be already wet, no problem

As Crush would say: just go with the flow...