Why wait so long to get married? Seems like you have one more reason than you did before. You can always have the big party in 2014, but you could get married in front of the judge in the meantime. Wouldn't even have to tell anyone if you don't want to.
I know how that is, with my first I felt that way. It was hard at first but they will get over it, it is get grandchild either way :) but I think you will feel better after telling her. You can wait until you're ready. But from experience, it's best not to wait too long, as my fiancé waited until I was 4 months to tell his family about our first and they were more upset about us not telling them sooner than the actual pregnancy. This time we didn't even hesitate. It won't be so bad, congrats and good luck!