"picking someone up of the aeroplane
?" Not so easy on the beach itself, but couple of easy options very close by. Either go NW and you can use the slip for the new car ferry to Eriskay, or the old jetty that used to be for the less recent passenger ferry to Sth Uist. (Keep an eye on the plotter/sounder through there though - pretty shallow, with large random 'lumps' of rock)
Or you can go south back towards Castlebay and pick someone up in/around Northbay (advantage there is that it's in the direction the bus from the 'airport' would go anyway).
Fuel available in Tiree if that helps. You can tie up to the ferry pier (Gott Bay?) and it's a short walk to the pump. We found an old shopping trolley on the pier which made it easier getting the cans back and forward.