For example, your children might not attend the same church they did growing up under your roof, but wouldn't you rather they worshiped with a different church than not at all? How you respond to this question says a lot more about you than you might think.
This topic is not in the realm of the theoretical for me personally. Our oldest son and his family joined the Anglican Church and our newlywed youngest son and his wife are members at a Baptist Church. We raised our children in churches associated with the American Restoration Movement.
I am happy that our children in these different congregations are active and participating on a weekly basis. I am of the opinion that the church isn't the building, the church is the people. Church isn't tied to an address or a location.
So if we disagree with a certain denomination/non-denominational church, what happens in that congregation might be more beneficial for your loved one than you know. Your loved one attending the church you don’t approve of will more than likely be singing songs to God, hearing Godly messages, and reading Scriptures. They might even be praying for all we know? I’m guessing there might even be a sense of community they experience there too?
But, you say, they are “being led astray by a false doctrine!” And, that church does “it” wrong, whatever “it” is, you fill in the blank. Perhaps, or maybe not. Maybe they are reading their Bible for themselves for the first time in their life, and comparing the Bible with what they hear weekly or with what they’ve been taught all their lives.
Unless we are a cult leader, we should never be afraid of people searching for the truth on their own, without us, or without our help. Children and people we care for or mentor need to have an ownership of their faith. They need to be able to defend what they believe, not because of what we say or think or because of what “our church” stands for, but because of the conclusions they draw from their own study and worship.
Who are we to limit how the Spirit moves within any congregation, or in the lives of our loved ones? Just because we are uncomfortable with it, or it’s too liberal/too conservative, it might be just where God wants your loved one. There’s no telling what they bring to the table from your tradition that can help that other church, just like there’s no telling how that loved one can grow in a different setting.
If someone leaves the congregation you worship with, this does not mean they have betrayed their faith or the Lord. Christians have gone in different directions over disagreements since the beginning, and God worked through those separations as well, consider Acts 15:36-41 "36 And after some days Paul said to Barnabas, “Let us return and visit the brothers in every city where we proclaimed the word of the Lord, and see how they are.” 37 Now Barnabas wanted to take with them John called Mark. 38 But Paul thought best not to take with them one who had withdrawn from them in Pamphylia and had not gone with them to the work. 39 And there arose a sharp disagreement, so that they separated from each other. Barnabas took Mark with him and sailed away to Cyprus, 40 but Paul chose Silas and departed, having been commended by the brothers to the grace of the Lord. 41 And he went through Syria and Cilicia, strengthening the churches."
Pray more than you pester. Scratch that, don’t pester at all, start to pray more. Ask nicer questions that show you are interested, instead of voicing harsh assumptions. Express your love more than your hatred or fears you’ve shared through the years. And, and this one is big, trust God more than you trust yourself to guide that other person you are so worried about.