Why hello there, Sarah! Welcome to planDIsney. We are so glad you've stopped by!
Your trip is fast approaching and I am sure you are so excited! I love hearing you are wanting to dress up with your daughters. The answer to your question really depends on how you are hoping to dress up. According to
Guest Courtesy and Attire Policies from the Park Rules and Regulations, costumes are only allowed for Guests 14 and younger. This doesn't mean that you can't get creative though! While adults cannot wear costumes, I have seen so many creative outfits that are inspired by a Guests favorite character.
It looks like the summer weather has finally decided to show up to southern California and while it may be nice and warm during the day, I always recommend an extra layer for early mornings and evenings once the sun goes down. I usually bring a backpack to accommodate that, but if you don't want to carry it around
renting a locker may be a great option for you. They are located outside of the park entrances of both parks, as well as inside each park as well.
Sarah, I hope you are able to figure out a way to get creative with your girls. See you real soon!
Carrie