My response:
Normally, no. Not unless there is an absolutely good reason, and then only with the court's permission (court order) to withdraw from such an account. Unless there is a court-recognized legitimate reason for such a withdrawal, that money stays put until the child is 18.
Good reason usually has something to do with emergency medical care, or putting a roof over that child's head, or the need to feed that child. Going on a "road trip" is not a good reason.
IAAL