Good on you leaving that church. My parents left our local church when I was 9 (for different reasons), and for the remainder of my childhood we had "church" at home. This was brilliant, and absolutely foundational to my understanding of scripture. "Church" for us was very simple - every Sunday morning everyone in the family would read the Bible for half an hour in silence. Everyone would have an understandable translation (young children would have bible story books, we even had a comic-book version of the Bible which was great). Afterwards we'd talk about what we learnt. Often we'd keep reading by choice as we were interested in what we'd been reading.
My parents also ensured we had an extensive amount of Answers In Genesis literature on Creation. We spent many hours reading this, and I actually learnt tonnes of science from it, leading in the end to my current career. But most importantly that taught me that the Bible is true and reliable, and we can actually believe exactly what it says.
And reading exactly what it says and following that rather than the words of man led me to realise very early on that there is nothing wrong with polygamy.
Just thought I'd mention this to encourage you that this can work. My one piece of caution is that you must keep it up. Our family "church" times worked well for a few years, then my parents became more slack about it and I found myself having to push to ensure that it actually continued for the benefit of my younger siblings. Don't let it slip, make sure you keep focussed on making sure both you and your children have regular times of Christian teaching directly from the Bible.