If different religions contradict each other, then they cannot be compatible.  In the Bible, it makes it clear that the free gift of Salvation provided by Jesus is all that is necessary to go to heaven.  Any other method is in vain.  However, as with the 1st century Christians, the goal is to get the good news out to everyone, so they can accept the gift of Salvation.  By not getting the Word out, and just sitting back and assuming that everyone will go to Heaven anyways, is being lazy, and not doing the intended duty of a Christian to get the message out.  The Bible says that in times past, those with good hearts but ignorant of the Word were not condemned, but that once they heard the message, it was their choice whether or not to accept it.  So the question you have to ask yourself now is, do you sit back and just hope everything will be alright anyways, or do you realize that that is not the case and take action?