There are three things you can not make a child do--eat sleep and go pee or poop when you want them to. (sigh)
I have two children. A son who trained himself at 4. I will tell you the story.
I went before his 4 year old preschool started in August to meet the teacher. I mentioned to her that my son was not toilet trained. She said, within earshot of him, that she usually did not take children who were not potty trained and never changed diapers. Well, all of his best friends were going to that school and there was no way he was not going to that school. So in two days, without me saying a word, or doing anything to help, he trained himself. Easiest thing I never did.
My daughter did a similar thing at 18 months only a trip to Vancouver and Victoria B.C. by boat, ferry, bus, and train, when we visited every clean and dirty restroom in sight whenever food entered her mouth. But was scared to go poop in the toilet--pee was okay. Poop--no way. But of course every time she ate she had to go poop. It was a four day trip. But she trained herself. It was easy to train but I wish it was at home.
I suggest you wait until you find they are motivated by something they really want to do or have that requires them to be potty trained. Then go after it. Have them be internally motivated, or motivated by circumstances from their life not motivated by you. It is much easirer on you.