might try in a small area at your backyard

Although the weed killers all claim to kill the weed only, your grass type matters too. Think about that, weed is very aggressive type. If you have bermuda grass which is aggressive by nature, you might win the battle to kill the weed without hurting the grass. If you have fescue, you might not be that lucky.

Worse worse, you can always reseed. IF you have cold-season grass, you can reseed in fall or spring (preferably in fall). If you have warm-season grass, you have to wait till early summer coz they go dormant in winter.