Women of Reform Judaism has a great deal of material available on how to write a Shabbat service, especially on how to write one with a group so that it is both a learning and a creative experience. In addition, there are many examples of Shabbat services which they could send you. Please get in contact with Women of Reform Judaism, (email@example.com).
By the way, if your women's group is not a member of WRJ, I suggest that you ask someone to come to your group to introduce you to the many advantages of membership in an international women's group affiliated with Reform Judaism. WRJ has a great deal to offer, and you probably have a great deal to offer WRJ.
Naida 87 Families
Women of Reform Judaism has many scripts available--see their Web site for a list with descriptions: http://rj.org/wrj. Aya 850 member units
Women of Reform Judaism has a couple of books called Covenant of the Heart and Covenant of the Soul which have readings related to liturgy from a woman's point of view. Another popular resource is Marcia Falk's The Book of Blessings. I have also found some wonderful things from Namoi Levi's books, although those may be more for "healing" than for services.
The key thing to remember when preparing a creative service is to follow the rubrics in their proper order. Remember that the shoresh (root) for siddur is the same as seder, which means it comes in a specific order. As Reform Jews we may omit certain parts (as an informed decision, of course), but what remains stays in its place.
Having women interested in creating a worship service means that you have a real "teachable moment"--an opportunity here to teach them about the structure of the service. Your rabbi or lay leader familiar with the service order and themes of each prayer can share that with the women. Then, you can show them that the WRJ collection of prayers is nothing more than things that women just like them have written. Ask them to think about a theme that is meaningful to them; something that they are grateful for--creation, redemption, revelation (new learnings), generational connections, holiness, etc. Have them pick one and then write a paragragh or two--prayers do not need to be poetry.
Once you have them compiled, it is not too hard to edit them into a series that contains both straight readings and responsive ones. You can insert meaningful music into the service where appropriate.
For years our WRJ group "wrote" their Shabbat service by compiling the words of others. For the past five years they have written their own each year; it has been amazingly empowering.