Is it permissible for me to
give to Christians books which contain aayaat of the Qur’aan that prove
the Oneness of Allaah, which are written in Arabic with the translation of
the meaning written in English?

Praise be to Allaah. 

Yes, it is permissible for you to give them books
containing aayaat from the Qur’aan and to use (these quotations) to
prove various issues, Tawheed and others, whether this is in Arabic or the
meanings are translated. This is a deed for which you are to be commended,
because giving them or lending them to them is a kind of conveying the
message and calling them to Allaah (da’wah). The one who does this will
be rewarded if his intention is sincere.