I believe you can possibly switch to the other park but you may have to pay any price difference. Call up the number for guest services and they will direct you better. Good luck. Enjoy the parks!
If I recall correctly, you have to use the raincheck at the park that gave it to you. The riles may have changed but that was my understanding with my ticket purchase. Hope this helps.
My apologies for my lack of knowledge. You must contact the Guest Services number given on your rain check for a specific answer. I have no experience with rainchecks and cannot offer a reliable response.
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