lake Should I cancel my Amex charge card?

I just opened an Amex Starwood CREDIT card and will use it as my new primary card. I've stopped using my Amex Green CHARGE card which I've had for 17 years. I'm debating whether I cancel the Amex Green card ($55 annual fee), but am concerned about a negative impact on my credit score (I have good credit and do not want to damage). Thanks.there