Set up your eSIM at home, on hotel WiFi, or on airport WiFi before you fly. You install it once and leave it switched off. When the plane lands at Hewanorra, you turn on data roaming for that one line and it finds the FLOW network on its own. No queue, no kiosk, no SIM card to swap.
Buy the eSIM days ahead if you can. You need internet to install it, and you do not want to be hunting for a signal the minute you arrive. Once it is loaded on your phone, it just sits there waiting for you to land.