My impression is that most Rabbanim and mechanchim say that one is supposed to grow slowly and take small steps. The main thing is that you are going in the right direction.
As such, it wouldn’t make sense to say that you are now creating a situation in which these people are sinning b’maized as opposed to before when they did not know better. They are doing what they are supposed to be doing and taking small steps.
By the way, you can also ask the same question about your own children. Since most people do lots of aveiros and are oiver on many halachos, isn’t it better to make sure not to educate your children so that they will be tinok shenishba?
The reason why it’s not (even though it might seem like it is) is because you are doing someone the biggest favor when you teach them about Yiddishkeit! In one of Rav Matisyahu Salomon’s sefarim, he raises the question: “Why should we do kiruv?” He brings several possible answers which he rejects. I believe he mentions the fact that they are tinok shenishba, so the reason for teaching them can’t be that they are obligated in the Mitzvos.
The answer that he ends up with is that teaching someone about Torah and Mitzvos is the biggest favor you can do for them.