But, bear in mind that if you say that something is necessary for the child's well-being and it cannot be provided, you may find yourself without travel arrangements. Carriers must rearrange seating by way of example. But, cabin crew are generally not permitted to provide special assistance and if what you can provide is not enough, you may be required to travel with an aide or somesuch.
Not in any way suggesting that you sugar coat the situation. Simply that one should list out the things which are necessary for safe travel and things that make the trip better.