You can add different prices for multiple categories like an adult, child, infant, etc. for a single trip using WP Travel free version. If you are willing to add different prices for multiple categories then you have to add a separate pricing option for different categories.
To set different prices for different categories like child, adult, infant, etc., you have to click the ‘Add Price’ button under the Prices & Dates section.
Also, regarding adding a pricing category by going to Admin Panel > Trips > Pricing Category
Then on the Booking page, different prices with different categories will be shown on the frontend as all multiple categories cannot be selected with the single pricing with WP Travel free version.
If you are willing to add the Multiple categories in a single pricing then please refer to the related Knowledge Base.
Further, if you have any queries, please submit them to our Contact page.