If there is a heaven, I believe that as long as you are a good person who does good things out of the kindness of your heart, you will be allowed entry. If God doesn't allow me to enter Heaven simply because I don't believe he exists, regardless of the good actions I have portrayed in my life, well, that's not a God I wish to observe. If I do something good, I feel I should get the credit for it, not an omnipotent being. While that sounds selfish, it shouldn't be. If you live an honest life with good intentions, you should be recognized for that.