You don't always need a proper reflector, just a white towel thrown on the ground in front of them will reflect light upwards, to help eliminate some shadows. Or even someone else just holding a piece of white cardboard or paper so the flash bounces off the roof and then off the towel or cardboard back up at them.
Of course this is very easy to say sitting at the computer, not as easy when you are relaxing at a BBQ. Sean is the expert in this regard not me, but light reflected at the right angle can take years and pounds off.
There is a real connection with the eyes of your subject and a relaxed feel to the portraits, again I think he should be very happy with these shots.