Keep the pregnancy under wraps for now. This is life changing, exciting news and you'll want to revel in your shared secret for a while. Choose a time to tell the grandparents-to-be and put together a plan. It is best to wait until you are at least a few weeks into your pregnancy before you spring the news. And be sure to break the news to both sets of parents with similar fanfare and timing. You want to avoid hurt feelings. As for announcements to friends, co-workers and acquaintances, common etiquette dictates that you wait until week twelve. But, do it whenever the time feels right, just make sure family knows first. The news will spread quickly since it's almost impossible to keep such exciting news a secret.
Make an appointment with your doctor now. Chances are that the home test was correct and everything is fine, but it is essential to see your doctor to set up your antenatal care.