Moving to a new place very often is something which can be pretty stressful for cockatiels (they are very much like parrots in that aspect). It takes time for them to get comfortable in their new surroundings. And then in your case there's new people they have to get used to, too! :O
Give them some time, and I think there's a good chance they'll come around
Did your friend tell you where the birds came from? Were they tame before, and did they step up and let their heads get scratched? Or have they always lived in an outside aviary and never had much contact with humans?
When I got Puck, I was advised to cuddle with him for a bit before introducing him to his new cage (he is a cuddlebug!) Otherwise I was told to leave him to do his own thing and get used to all the new things in his life in the week or so following. I did pet him during that time, but only when he came to me of his own free will.
Give your new feathered friends some time to get used to things, and try to maybe bribe them into coming to you by offering millet from your hand.