You were just proposed to by your boyfriend and you are excited! One problem: He hasn't met your family yet!!

[edit] Steps

Gather all of your immediate family together. When you have gathered them all together, tell your family that you and your boyfriend are getting married.
Tell them about your fiance. Tell them about his: his age, career, activities, hobbies, personality, friends, where he lives and what he likes.
Talk to your fiance. Tell him what your family is like: your parents siblings (if you have any), where they live, what kind of a place they live and what your parents do for a job.
Ask your spouse and family if any of them are busy. It is very crucial to know whether or not they are busy. First, ask your spouse and then your family.
Plan 'the meet'. Call up your whole or (just immediate) family and plan a cook out; a vacation somewhere nice or just a simple outing.
Relax and be calm. Reassure yourself that everything is going to be as perfect as it will go.

[edit] Tips

It might be a good idea if you stay at your parents home than at a hotel, if there's room.
Try and relax your fiance if they are nervous. Tell them it is going to be great and that you will love them.