Keep three things in mind when you are writing a ritual for a small group:
1. Let the Divine guide you throughout the entire process. The rituals we perform are in honor of our Lord and Lady and, therefore, Their guidance is key to its success.
2. Keep ALL participants in mind when you are writing the ritual. Think about each person and ask yourself...what do we all need right now?
3. Keep it simple and don't demand perfection from any member of your group, especially yourself. It's very easy to get caught up in the "actions" of a ritual and lose the "emotions" which are supposed to come from it.
Other than that... relax, breathe, and embrace your role.
Much luck and many blessings to all of you!