Aiming to bless people is a perfectly legitimate aim, and I can enjoy the doing of it and take great pleasure in having done the Father's will and having done a good job at it, all whether or not someone becomes a Christian because of it. This is reflected in all of Matthew 25, but particularly in the parable of the sheep and the goats. (Jesus takes how we treat his brothers personally (Thanks David Cook for the phrase)).)
How cool is our God? He's the one who does the saving, and yet by no means does the worker lose his reward. He's the God who saves us with no desert on our part, and yet the God who will give to each as he deserves, and there is no partiality.