OK here goes. I apologise in in advance if questions is really stupid. My husband and I run a charity. The charity doesn't have much money so we use our personal iPhone (with shared apple-id) to do personal stuff as well as charity work. The charity bought another iPhone for another charity worker to use. The three of us need to be able to share all the Charity contacts which I have in special contact groups. At the moment this other worker shares our apple-id. It makes me nervous though 'cause she can see all our personal photos and contacts not related to the Charity. How do I get around this? And how could it work for other charity workers? Also we need to send out a lot of large group texts (as our charity recipients don't use email). Is there an App you'd recommend? The GroupText one I use doesn't have much flexibility.
Don't keep the contacts you want to share in iCloud. Use, for instance, a GMail user, and keep the contents there. All three of you sync the GMail contacts list.
Honestly, this is a situation you should never have got yourself into in the first place.
Not only are you sharing contact details with this, hopefully trustworthy, third party, you are also sharing all your online passwords & other security details that iCloud remembers for you, including any bank cards you have saved into the system & additionally they have access to any apps you have purchased & any data those apps may store as part of your ID.
It is not even recommended to use the same Apple ID in the same family.
Instead you should use Family Sharing for yourself & your husband, which enables the sharing of some data, but not all & as already stated by Marc, use some 3rd party contacts system, Gmail etc to share just the required set of contacts.