Gluten is a protein and binding agent that can be found in wheat and other grains like barley or rye. It helps dough to have an elastic type texture, and will help the dough rise and give a chewy texture. When substituting for gluten when cooking with gluten free flour, you add an ingredient called xanthan gum (there are other stabilizers, but this is my personal favorite as I think it turns out the best results). The xanthan gum will replace the gluten and does not affect people with celiac disease. Xanthan gum will add volume to your recipes and make sure that the product doesn't come out crumbly.
People with Celiac disease have a stomach lining that when exposed to the gluten toxin, affects their intestinal villi (villi are fingerlike projections that protrude from the intestinal lining that increase absorption). When exposed to gluten, the villi will shorten, swell and poorly function thus leading to malabsorption in this population.
I would also ask your friends how sensitive they are. Some people, even having a little wheat in the house can upset their lining. If you do decide to try to the new recipes (which I think is a great idea and fun!), make sure that you keep the gluten free flour away from any wheat products.
personal experience that has helped me convert my recipes to gluten free I do not have Celiac, but I have switched over to a gluten free diet, and I will say that it has been great. I do have more energy, and I just feel better overall. If you have the right recipe, gluten free meals/snacks/desserts, can be just as tasty if not tastier than gluten products.