Arrange for the system to calculate the costs for adults and children from the beginning of the search until the checkout so that the user sees the final price.

For example, the BOOKING.COM website calculates all the prices of the selected items.

For example: you do not calculate the maintenance cost of the hotel room, you allow pricing only a general price without considering the number of people or price by type of person.

On each hotel reservation site, a general price for the room is defined, then each person's supplement is added to the general price of the hotel room.

I don't understand what you tried to do in the template, but that's not how any hotel booking website works.