I am thrilled for you getting your first Yorkie. It sounds like you have a terrific family. One of my sisters had long haired Chihuahuas for years, before getting her first Yorkie. Now she has both and swears her family is just perfect now.
Brushing teeth just takes practice. I don't lift their lip. I taught my pups to let me brush up and down on their back teeth when they are covered with the jaw skin. The front teeth are easy. At first I used the finger tooth brush, then moved up to a child's soft brush. Some people on YT have trained their dog to accept an electric tooth brush and even a water pick ! I guess with enough patience you can teach a Yorkie to do just about everything a human toddler does except bathe, dress, and brush their own teeth ! Best wishes and welcome to Yorkie Talk.