Checkout Calculation with tour variation

Hi,
I’ve been working on a website, with this theme, which sells tour packages and I recently came across an issue on the checkout page.
We have two variants of a tour (With flight and Without flight) with a different price.
I’m having a problem with the calculation on the checkout.
[Screenshot] https://s3.amazonaws.com/travel-wp-nepal-tours/nepal-tours.png

I’ve set the cost of a tour without flight as a default price and added a checkbox for ‘With Flight’ as a variant. If the user checks this option then, it should be applied for all the tickets but this is not the case here.

Could you please suggest what can be done in this case?
I’ve seen similar issues raised on the forum as well but the replies have been marked as private. http://support.physcode.com/forums/topic/link-tour-variations-to-the-total-number-of-tickets/

Please let me know if I’m not clear.

Thanks.