It would depend on whether your parenting plan established shared or sole parental responsibility. If you have Shared, then yes. You would need to at least consult with him on the issue. If he doesn’t agree, you can enroll the child, but try not to have it on occur on his parenting time with your daughter. He isn’t required to take the child tot he class or pay for it unless he agreed to her enrollment. Most parenting plans require that if the parent agreed to the enrollment, he/she must take the child to the activity. If you have sole parental responsibility, you can enroll the child without discussing the matter with the other parent.