Id keep it from them until theres no way out of it any longer, then when or if they moaned about it id say id kept it from you because i knew your reaction would be negative.
As a parent, I have to say lying to them is NOT worth it. You end up spending more time making lies for lies. If you want to save the pain of that alone letting them know is good. Now the question is .. what is the reason for them knowing. If this is online and 1+ hours away then you have some issues. Esp if your young. This isnt just a parent thing this is a you and him thing. How long can you two really hold out being at a distance. You wanting to go do things with friends and your bf is not there. Your friends talking about thier bf and you wont have much to say. Theres alot to think about. I personally think telling them is easier then hiding and if things are good (meaning your good and hes good) they just might be open to the distance.