What's the difference between "Children of God" and "Servant/Slave of God"?

Christians say we are children of God. Muslims say we are servants/slaves of God. But both describe us as having to obey him so... a person can be a servant of God and A Child of God right? But the problem with being a "child" of God is that is ascribes overtly human aspects to Him, namely family wise.
But why does a person need to think they are in a "family" with God to feel like God loves them?

These are my thoughts/ramblings on the subject.

What are your opinions on it? Which one is more befitting of God?