If you don't want to enter the child's price as a percentage discount from the adult's share of the price, you can enter the child's price as an absolute amount.
Example: The price for a 1-night stay for 4 people is 4,000 CZK (i.e. 1,000 CZK per person). We want to set the price per child at 500 CZK.
First, we will change the method of entering the discount in:
Settings - System settings - Child discount entry method - enter price per child
Then in the Prices module we display "restrictions" and enter a child discount in an absolute amount, e.g. CZK 500.
The price for a 1-night stay for 4 people, including 1 child in this case, will be CZK 3,500.