I would suggest designing different types of retreats. Have some that are shorter (a weekend, or even just a day), some that are longer (long weekend or weeklong, maybe even 2-weeks); some that are more structured and others that are less structured; some that are themed and some that are "pick your own;" maybe even just have a quilter's B&B option where people can stay and make use of certain parts of the facility (like a couple of open sewing rooms, a quilter's library, or a space for designing) and sew in peace without kids, spouses, work, or whatever other interruptions and stresses happen at home.
Have kits available, or allow people to bring their own supplies; some materials available to rent (like sewing machines) or some that are free to borrow with the price of the retreat.
And depending on your location, you may want to see if you can offer some organized side trips or shuttle service to either local quilt/craft shops or fairs, or even just to certain local tourist attractions.
Now... having said that, I'll add the caveat that you should definitely not have so many different packages that you can't manage them all!!! Start out with fewer options and work within your abilities and resources.