I looked into it and, personally, I'd save your money. The reason I say this is cause just about every child we've seen in their dresses at the parks are miserable and the dress is dirty. To get the dress, you have to do the ~$189 package. Those dresses are about $50 at the Disney store at the mall. The hair style is a simple bun with glitter spray($5 at claires) or with funky braid scrunchie hair($4 at most stores). As for sashes, you can also get those at claires for about $5 a piece. I looked into it cause the Pirate version is so cheap but the princess one is just nuts. I'd rather have princess time with my DDs myself and do their hair is really great styles with glitter AND color sprays and get sashes and tiaras from claires. Im not doing the dresses at all as, like I said, they get ruined. I'd be upset if a $189 dress had juice running down the front, dirt at the knees, and a tear on the chest KWIM? Costumes don't clean easily. My girls would be really upset that it was ruined, too. Also, both of your girls would be able to do it together. I have a 2yr old that loves to be like her 6yr old sister but wouldn't be able to participate. Doing it with them gets them both some mommy time while getting to do it together and maybe even spray and "do" each other up!
I plan to take a kit. I will have hair glitter, hair color sprays, tiaras, sashes, real make up in little girl colors with tutus. They will do each other up (with mommy's help) in our rooms. they will have just as much fun, if not more, than going to a strange place having some stranger pulling on their hair(my girls have tight curls) and a bunch of other kids running around so they can't really get attention.