Actually this is practised in Arab countries such as Yemen also, I was surprised myself when I saw my friend in Yemen bowing down and touching her elders feet, but it's haram because:
First of all, even though this is 'tradition' and in Islam it is allowed to follow our tradition as long as it doesn't go against Islam, We know that this is a known Hindu tradition which goes clearly against Islam....and we as Muslims were commanded not to follow the disbeleivers.
Secondly, this goes against the rulings of Islam where we are NOT to bow ourselves towards anyone else besides Allah Subhanah. Rasululllah peace be upon him said " If I was to order anyone to bow towards anyone else, I would have ordered the woman to bow towards her husband"
There is a story about a Sahabi ( or Taabi'ee I can't recall) who went to see a King.The King knew of the Islamic prohibition of bowing towards others, so he constructed a low door and placed his throne in front of it, so that when the Sahaabi entered the door he would have to bend his body. When the Sahaabi saw this, he turned around and entered back first so as not to go against Rasulullahs teachings.
I would suggest you inform your family about this in the most nice and polite manner Insha'allah and make clear to them that Islam comes before tradition no matter what. And remind them also of the hadeeth "There is to be no Obedience towards mankind, if it is in Disobedience towards the Creator"
