Does he want an art school/BFA? That will be more narrowly focused on the visual arts/animation without so much creative writing. Some schools will have a BFA in creative writing but often it is part of or a concentration within an English major.
Because the original post mentioned interest in both visual arts and writing, and asked about open curriculum schools, certain liberal arts schools came to mind (like Bennington).
If the original poster wants an art school, it would be great to clarify that, but that was not the impression I got.
There is a great book obtainable online, entitled “Creative Colleges.” It lists schools that are good for music, theater visual arts, film and writing, as I remember.
Other thoughts; Skidmore in NY (very artsy) Kenyon in Ohio (known for writing), Clark in MA, Macalaster, Hobart William-Smith, Vassar, along with Bennington, Marlboro, Sarah Lawrence, Hampshire (requires maturity), Goucher, Lesley (gorgeous new art building), Brown, Amherst.
Look at Colleges that Change Lives- a website and book and national fairs. Loren Pope also wrote a book that is now a bit dated, entitled “Looking Beyond the ivy League,” which is still useful in its lists of schools for different interests.
For a kid like this, there are many many schools that would fit the bill, but I would think actual art schools might be too narrow in curriculum for him, as well as structured. He could attend art school and do writing on the side, but it would seem that with multiple interests, an artsy liberal arts college would be the best way to go. Even some state universities might fit the bill, though they would not have an open curriculum (but are financial safeties for many).