Little kids tend to be embarassingly honest, so "young miss Auntie" would blow granny’s cover the minute she tried to show off. Could be fun to watch…
Remember, your identity is in no way connected to granny OR anything she can say about you, true of false. You’re Alex’s mom, and you have a responsibility to raise him to appreciate who he is and where he came from.
So go for it and enjoy yourself…and take pictures!