Ajnea,

How old are they? When you buy the flight ticket from KTM, also book the wheelchear. It is free of cost.  Please write down them info. in a paper and tell them to show to airhostage every time they in and out from flight.

Please write on top of the paper HELP (bhangera tauke letter) and also write we cann't read and write english. Last year I had same situation. Please be sure the wheechear is booked. Ask couple time in KTM it is booked or not. 

Goodluck