I would like to first say to my brothers and sisters to please excuse me for my manners I forgot to say:
assalaamu alaikum
and walaikum assalaam brother Khaleel
Well brother this is some what easy to answer but it deepends on your situation if it will be something easy for you to do.
Remember what Allah says in the Quran :
بِسْمِ اللّهِ الرَّحْمَنِ الرَّحِيمِ
يَا أَيُّهَا النَّاسُ اتَّقُواْ رَبَّكُمُ الَّذِي خَلَقَكُم مِّن نَّفْسٍ وَاحِدَةٍ وَخَلَقَ مِنْهَا زَوْجَهَا وَبَثَّ مِنْهُمَا رِجَالاً كَثِيرًا وَنِسَاء وَاتَّقُواْ اللّهَ الَّذِي تَسَاءلُونَ بِهِ وَالأَرْحَامَ إِنَّ اللّهَ كَانَ عَلَيْكُمْ رَقِيبًا (1)
O Mankind ! Fear your Lord who created you all from one single soul (Adam) and He created from it (the soul of Adam) its spouse and produced from them both many men and women; So fear Allah whom you are duty bound and the wombs (that bore you) ! Verily Allah is watching over you (4:1)
Regardless if your mother is Christian, Jewish etc you have a duty towards her, and you must respect her by all means. She comes before your father. Obey your parents by all means except when they tell you to do something against the will of Allah you are to disobey them in a polite manner.
You must be kind to them and gentle no matter what even if they find out you are muslims humble your self to them and speak to them with words of kindness. Follow the example of Jesus in the Quran he protected his mother by all means and was her helper.
Show likewise the same to your father but if it ever came to a choice your mother comes first before your father.
Let Islam be manifested in your character for their eyes to behold and for their hearts to be held in awe.
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Brother I know what you mean, I had to go through the same transition with my family years ago. they invested in me with Christian school then all of a sudden I converted to Judaism on them. They didnt take it lightley at all. Then years later in college I became a Believing Muslim. Thus they took the hardest cause they had soo much enmity towards islam. But knowing me I was bold and didnt care. After a period of time they accepted what I had become and respected it and didnt try to revert me.
I went through battles with them indeed, but I never lost the respect for them though regardless what they may say about islam, in this is blessing and fitnah ~ test for you and them.
Remember how the Prophet (s.a.w.) still treated his uncle who remained a mushrik.
All I can tell you brother is let them detect the change in your character before you tell them your muslim if you know how they feel about islam.