Hello @shifuhotman,
Thank you for contacting WP Travel Engine team!
While checking your site, I was not able to replicate the issue you mentioned, i.e., I was able to calculate the price correctly when selecting more than one adult and child. You can check this screen recording link.
If you are still facing issues, please provide us with a specific screen recording of the issue you are encountering so that I can inspect it and provide you with an appropriate solution.
Additionally, please verify the issue by clearing your cache and checking on different browsers.
Looking forward to hearing from you.
Thank you!