Carrie Underwood has been having the time of her life during her Las Vegas residency.MORE: Carrie Underwood's tasseled dress may be her most daring yetThe country singer has had fans from around the world coming to watch her perform at the brand-new Resorts World Theatre.And over the weekend, the award-winning star had two very important people come to see her on stage – her young sons Isaiah and Jacob.VIDEO: Watch Carrie Underwood's sons dance to their famous mom's music The two little boys