Mrs. Helen Tobin, widow of Gov. Maurice J. Tobin, said yesterday that she will be married to John F. Regan, New York labor leader and widower, "sometime late this winter." The Tobin and Regan families have been friends for years, both summering in Scituate. Regan's late wife, the former Ellen Galvin of Charlestown, was a sister of William J. Galvin, superintendent of the Market Division and former Boston city councilman. Galvin and his brother, Michael, who served as an undersecretary of labor with Tobin in Washington, were long associated in politics with Tobin.