What would Buddha advise to farewell when one of your parents died?
You can do transfer of merit. 

More on this see:


How can merit be transferred?
Transfering merits
Sharing merit in Theravada Buddhism
Actions taken to transfer merit
Does Theravada believe in feeding food to hungry ghosts?


Also you can do a:


offering of cloths to the monks in memory of the dead (monks cloths were initially made of the cloth used to wrap the dead bodies)
organise a dhamma talk for the benefit of the dead (generally the night before the almsgiving mentioned below)
organise an almsgiving for the benefit of the dead (generally at 7 days, 3 months, then annually)


Some of these are covered in: Buddhist Ceremonies and Rituals of Sri Lanka by A.G.S. Kariyawasam