I have tried to do exactly as you suggest and deleted the printer and re-installed it. The option selected was USB out of the two which were offered - the other being Scanner. I can see no reference Kind under Options and none to AirPrint. The 2 sided printing is still greyed out (no change at all that I could see) so I selected the suggested download on the off-chance that it would help matters. The download suggested on the next screen was a WF-xxxx so I assume this is for a different printer - mine is ET-2750- and have no idea if it would work for my printer and computer combination. Perhaps you can advise?
I have no idea how to check how the printer is connected to my computer - as far as I am aware it is via the USB cable and I have not seen any reference to AirPrint in all the efforts I have made.
The file which was downloaded when I first installed the printer is Epson_ET-2750_Series_LM_10_Web.dmg. Is this the correct one, and if not how do I find the right one?