See
here. A number of companies are located on-airport in HNL, but Alamo is not one of them. You might want to get an updated quote to see if any of the on-airport companies are less expensive as that will reduce risk and increase convenience. You can also make a backup reservation with an on-airport company just in case you're running late.
Another recommendation is that if you're cutting it close, call Alamo at (808) 833-4585 as soon as you're wheels-down and let them know you're on your way.
Keep in mind that many companies allow spouses to drive for free including Avis, Budget and Enterprise as well as Hertz and National with free loyalty program membership. More info on that
here.