Scheduling Tool - Jet Ski Tours

Hello all,

I'm trying to use the scheduling tool for a client that has a jet ski tour company.

He has 4 jet skis available. 1 tour per day. 

Each jet ski can hold up to 1 driver and 1 passenger.

Customers pay a different price for a driver vs a passenger.

I need a way for customers to choose the amount of drivers they have and the amount of passengers they have and get an accurate price.

Right now I set it up as a group class, with 4 spots available. That works great for the driver portion but adding passengers is where I'm having trouble. 

Setting passengers as an "add-on" adds that number of passengers to EACH driver.

If they reserve 2 driver spots and 2 passenger spots, the scheduling tool will add 2 passengers to each driver, giving an inaccurate price. 

Is there a way to allow customers to add-on the number of passengers they have to their entire booking and not have it add per driver spot that they reserve?

Thanks!