Hey there Hoai-An,
Welcome back to planDisney! Thank you so much for your question - I'm thrilled to see that you have a trip to the Disneyland Resort coming up in just a few short weeks!
You're doing some great planning - rest days can be really helpful when visiting the Happiest Place on Earth with all the walking involved.
Theme park reservations can be made and changed at any point as long as there are reservations available. However, it is possible for them to run out, which would mean you would not be able to visit that park on that day (if no reservations are available).
My recommendation would be to make a theme park reservation for the day that you feel most confident about, just to make sure it's secured. Then, as you get closer to your visit, if you change your mind then you can change your theme park reservation through the
My Plans hub on the Disneyland Resort website. I'd just hate for you to wait too long and for theme park reservations to run out for the park you were hoping to visit!
Thanks again for your question, Hoai-An! I hope you have a fantastic trip to the Disneyland Resort!
Have a Magical Day,
Greg