I asked my bf now my husband how he told his parents about me. He said, well they knew that we were penpals for quite some time, so after few years of correspondence, we then decided to meet each other in flesh and he told them: "Mum & Dad, I've booked my flights to the Philippines."

BY THEN, they knew we were serious about our relationship.

They did not oppose or anything (think they knew it would happen eventually)
My husband is a very private person, he isn't that type who will "Kiss and tell" nor actively participates in chit-chats. So yeah, I think it helps when you keep it in private first, not telling anyone until you know it's for real. Also, the more people involved, the more they will "cricize". Less talk, less mistake as they said.