The 66-year-old will walk down the aisle with Medvetz, 42, this autumn, in a small chapel in Las Vegas, reported Sun online.
"Cher and Tim plan to hop on the back of a chopper this fall and take off on a road trip that will end at a Vegas wedding chapel," a source said.
Apparently, it was her sons Chaz, 43, and Elijah Blue, 36, who convinced her to marry with Medvetz.
"This is Cher's last chance at love, and she has her sons Chaz and Elijah Blue to thank," the source added.
The singer has been married to late Sonny Bono who is Chaz's father and later wed musician Gregg Allman, father of Elijah Blue, but both marriages ended in a divorce.
Cher and Medvetz intend to have a road trip to Vegas before tying the knot there.