Albert Grannon, 77, will appear at Hull Magistrates Court tomorrow.
He also faces an allegation of possessing a firearm without a certificate.
Stanley died following an incident in Sproatley on July 26, 2018.
A Humberside Police spokeswoman said: "A man has been summonsed to court to face allegations of manslaughter and section 1 possession of a firearm without a certificate.
"It follows the death of six-year-old Stanley Metcalf during an incident in Sproatley in East Yorkshire on Thursday 26 July 2018.
"77-year-old Albert Grannon has been served the summons, and is due before Hull Magistrates Court on Thursday 2 May.
"We must remind members of the media that this case is now active."