Britney Spears’ two estranged sons, Jayden James, 18, and Sean Preston Federline, 19, are officially both legal adults — but she’ll never stop being their mama. The Princess of Pop reportedly plans to keep giving her boys money despite no longer being legally obligated to send her ex-husband Kevin Federline — who has primary custody of the teenagers — cash after Jayden graduates high school in November. “Britney’s on this crusade to spoil them,” a source recently spilled to a news publication of the “Toxic” singer — who first lost custody of her children in 2007 after a series of public mental…