Most senior parks are for adult over the age of 55, or at least one person in the unit over 55 in some parks. All parks will allow visitation by friends and relatives and children and families, and they have policies about such visitation and use of facilities.
You didn't say if you are interested in an all age park or over 55 park. I believe one of the parks in Windsor that's a senior park converted to a non-profit status, which may be what you are referring to. Please drop me an email and I'll be happy to make some calls for you to the management offices to help you find a park you'd be interested in. I have sold and listed many manufactured homes throughout Sonoma County. Please check out my blog for Mobile Home Info or ask me to send you a current list of homes in your price range. Thanks, Terry
By C0-Op do you mean that you own the land and share the common area like a PUD or Condo. There is a move by many MBH park owners to offer this to park residents. It is meeting with resistance in come cases as residents are fearful of higher costs and loss of rent controls for long term benefits. There are a couple of places in Sonoma County where this has happened and from what I see, most residents like being a land owner, even if they pay a common area fee for pool, clubhouse and maintenance.