As time goes by, you may want to formalize this arrangement. The group can set goals. They can decide to add a Shabbat service before or after dinner. They can decide to celebrate some of the holidays together or to hold educational activities for the children. Whatever the decision, make sure that the goals are realistic and achievable.
Unrealistic expectations can lead to frustration and discord.
Depending on your orientation, becoming a full fledged institution may be the best or worst outcome of this small Shabbat dinner in your living room. Keep in the back of your mind where you want this group to go. If you are content to keep the group small and intimate do so. Your connection to members of the group will be more intense and your religious experience more hands on. If you feel that you want to institutionalize the group, know that you will lose control and the excitement of being part of an extended family.