My parents left the Church

Those are all fair questions.

 
Let’s break this down. 

The first thing I would try to do, is to find out whose fault was your parents' church-exit.

Just like when you hear of a couple that have broken apart, one or both people are to blame.

 
When someone leaves the church...which party has departed from God’s-will?

The church member that left, or the church member that stayed?
I have seen many churches split over doctrine issues and other churches be formed. 

It happens, someone is always outside of God’s will.

 
Remember in the Book of Acts chapters 13-15, when John Mark abandoned the Evangelism team in Pamphylia that Paul and Barnabas were on? 

Then sometime later, he came back like a prodigal son and was ready to go again. 

Paul didn’t trust him, but Barnabas did and spoke up for John Mark. 

Paul and Barnabas argued and split up over John Mark, thus two evangelism teams were formed. 

The disagreement was not God’s will. But God used it to His benefit.

 
Your parents left the church and now you need to decide how to live.

You fear that if you make your way back to God, your parents may be displeased?

 
That may be true. 

If you are an adult, you need to follow the best course in life, which would be to follow Christ.
If your parents object, let them decide if you are still welcome to visit them,

or if they prefer you stay away.

 
Brave people will give away their family to follow Christ. 

And this article is one way to approach your parents with your decision to re-follow Christ.