Re
"It's a bit hard when the wife is in a wheelchair.
She likes to participate and is really interested in droning as well.
Ever tried to push a chair in sand.?????"
not being sarcastic or anything but would pulling the wheel chair help in sand. From pushing my Mum around, pushing tends to add weight to the chair whereas pulling might reduce the weight as you are tending to lift it. I am not suggesting it would be a solution for a long stretch of sand but it might work for short stretches. I don't know if sand could get into bearings etc.
I have also seen wheel chairs with wide tyres for soft ground, even balloon tyres, would they have any for hire/use at the beach? If so would they have somewhere secure to store your own chair whilst your wife was in the other one?