Generally speaking, babies under 3 years old may be allowed to enter the stadium for free, or they need to buy specific tickets, while children between 3 and 12 years old can usually buy children's tickets, and the price is usually between 50% and 70% of the adult fare. The specific discount strength may vary from region to region.
In addition, some cinemas may define the scope of use of children's tickets according to their height. For example, children whose height exceeds a certain standard (such as 120cm) may need to buy adult tickets. It should be noted that the charging standards for children's tickets in different theaters may be different, depending on the standards published by each theater.
The above information is for reference only. I suggest you get more detailed information from official channels.