Since relegation from the second tier in 2018, the Black Cats have failed to finish in the top two in League One, this year's fifth-placed finish earning a third shot at the playoffs.
Embleton's opener came as early as the 12th minute, the homegrown midfielder running from the halfway line before seeing his long-range strike diverted into the net by goalkeeper David Stockdale, who should have saved the effort.
To their credit, Wycombe stayed in the contest until the closing stages, but Stewart sealed the win 11 minutes from time with a low finish from the edge of the area for his 26th goal of the season.
Adebayo Akinfenwa was introduced off the substitutes' bench for the final game of his career as Wycombe pushed more men forward, although it made little difference with their opponents instead squandering chances at the other end to further extend their lead.
Nevertheless, Sunderland still comfortably closed out the contest, manager Alex Neil delivering his 11th win from 19 matches since his appointment in February.