Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Alamo car class in PHX for golf trip

My husband and are going to PHX this coming weekend for a golf trip and got a terrific rate for a convertible through Alamo's Hot Deals and applying a Costco coupon ($125 including tax). I am however nervous that a convertible will not fit our two golf travel bags and one large suitcase. What happens if we get there and cannot fit everything in the convertible? Would be able to change car classes no charge? Would we be able to change to an Intermediate SUV providing they have stock? One more question, do I have to print the Costco coupon and bring it to the counter or can I self-check in?
Thanks for any help/advice!

My husband and are going to PHX this coming weekend for a golf trip and got a terrific rate for a convertible through Alamo's Hot Deals and applying a Costco coupon ($125 including tax). I am however nervous that a convertible will not fit our two golf travel bags and one large suitcase. What happens if we get there and cannot fit everything in the convertible? Would be able to change car classes no charge? Would we be able to change to an Intermediate SUV providing they have stock? One more question, do I have to print the Costco coupon and bring it to the counter or can I self-check in?
Thanks for any help/advice!

You are kidding right, very slim chance of a free upgrade.