Hi there Jean,
Thank you for visiting us here at the Disney Parks Moms Panel. I hope you are having a practically perfect day.
Your question is a tad difficult to answer. Children visiting the Disneyland Resort can dress in costume every day if their hearts desire. However, Adult Guests are only permitted to dress in costume during Mickey’s Halloween Party. (That’s one of the huge perks for me personally!) With your
Mickey’s Halloween Party ticket, Guest can enter the park
up to 3 hours prior to the party starting, which is when Guests of
all ages may enjoy Disneyland Park in costume.
Since you are planning to be at rope drop on the same day you are attending this special event, I suggest renting a locker to stow your costume(s) until that 3 hour prior-to-the-party-time. Or what we did last year was attend rope drop and play in the parks and then head back to our hotel to change into our costumes when the Guests attending the party could enter for it. I think it worked out well because it was a very hot day and some of our costumes were better suited for the evening when it was cooler outside.
I hope this helps and that you all have a Boo-tastic time. If you have any more questions, please feel free to ask me, I'm here to help you plan your magical vacation!
Wishing you 999 Happy Haunts!
~ Lynette