Both ex-Arsenal players were substitutes in the shootout loss, with Heaven making his debut for United on the night.
"They are players with talent and then, when you have this moment with some injuries, they have to be ready," Amorim said. "It's our tradition to put players in to play, especially in this moment.
"We have to focus on everything, the future is right there and the young kids can feel the club and can change things sometimes for us, without buying players.
"And I think Chido did really well today. Of course, he was a little bit naïve in some moments, but you felt that, inside the box, he wants the ball – something the strikers have and he has.
"Ayden was really relaxed during the game so I’m quite happy for them but it’s a tough first (home) game for them."