As far as access is concerned, there should be no problem
As others have advised, there will be such a crush that ages are not checked.
Just make sure the girls have a mobile each, with each other's numbers, and your number programmed in, should they get separated.
Make sure they have secure bags with them - a zip or clasp top is best, and that they take as little money as possible with them.
Other than that, they should be fine.