DC has made Alfred into a jackass and an idiot if he thinks this will work.
First he goes against his own morals to bring together untrained kids to act as Robins. He refuses to let any of Bruces' sons see him without pretending to be someone else as seen in Grayson #12. Now he painted over the portrait done in Batman and Robin? Granted I never liked that thing since it showed a particular bias but why have it at all? Just it's presence raises too many questions and will piss everyone off once they see what was done to it. Seeing it now must make Bruce think he's full of himself to the point he wants a massive painting of himself.
This moronic ruse can't last forever because there are many factors Alfred can't control. Because others do know about Bruces' kids, I'm shocked Julia hasn't mentioned them.
"Hey Bruce, when am I going to meet this ten year old son you have? Don't you also have an adopted son somewhere? By the way I'm sorry you lost two of your sons and one of them was unmasked as Nightwing."
Okay some of that is blunter than normal but someone would bring these things up. Alfred is being cruel to all the boys by taking away their legacy to give to strangers and forcing them out of Bruces' life. He's always been the biggest supporter of them all being family and now he's pushing them all to the side.