And actually it is discrimination. Against those who don't have children, and those that earn more than others.
discrimination: to make a distinction in favor of or against a person or thing on the basis of the group, class, or category to which the person or thing belongs rather than according to actual merit; show partiality
Many childless people will be getting the bonus.
In the case of welfare and tax cuts 'merit' is the 'quality' of having an income that is deemed worthy of needing the tax cut/handout.

The tax system isn't a bank account where we make deposits in order to be able to withdraw later.