How can I set different prices for children and adults?

Open the resource settings.
Set the total share count—the total number of adult and children’s tickets.
In this example, it is 20.

Next, create two shared price options: Children and Adult.
Set a lower price for the children’s price option than for the adult price option.

If you want both 20 adult and 20 children’s tickets to be available for booking, set the Share count to 20 in both price options.

As a result, your configuration will look like this:

You can also strictly allocate the total number of tickets between adults and children.
For example, allow booking up to 5 children’s tickets and 15 adult tickets.
To do this, set the Share count in the children’s price option to 5,
and in the adult price option to 15.

In this case, the configuration will look like this:

See this example in action: