found this:

We are looking for William, who is
a huge part of the movie. Since the character is five years old, we
would be interested in seeing anyone from the age of 5 to 8, of
course, looking for very young looking 8 year olds.

William: to play 5 years old, male, Caucasian. A serious child.
Raised in Manhattan, William is a precocious, know-it-all preschooler
that tests his step-mom's patience with his unending questions.

The child should be very verbal and bright. In the film, he's not
necessarily a social kid...he's almost intellectual and dry. We are
going to have a day where we open our office for people to bring their
children for us to meet them as the first step. The child who plays
the role does not necessarily have to have experience, but will need
to learn lines and understand instructions.

Friday, September 5 - 11-5pm
Telsey and Company Casting
311 West 43rd Street, 10th Floor
New York, NY 10036