I want to use 'family sharing' but I want to keep my contacts separate as my children have no need to use my work contacts and vice versa. Can someone advise?

Again, Family Sharing DOES NOT share contacts. So there's nothing to be done to not share them.

If you were sharing contacts and deletion on one device caused deletion on another , then something else was happening and we would need to know what to offer any kind of advice.

Were you using the same Apple ID on both devices? Where were the contacts deleted? the device? iCloud directly?

In other words what exactly happened?

Not sure I understand. Family Sharing Shares purchases, Calendars, and photos. Contacts are not shared through Family sharing.

my wife deleting his contacts, then I found that my work contacts had been deleted along with it!

You might want to inquire into the details of what was done.

No one is upset. Just pointing out how it works, the same way you did, with an uppercase word.

If you do not want to share your contacts, you can either stop using the same Apple Id on all devices or turn off Contacts in iCloud Settings for each device you do not want to have your contacts on.

Settings->iCloud->Contacts->Off

Alternatively, you can completely sign out of iCloud on other devices, while keeping the same Apple ID for the iTunes & App Stores, so you keep access to all the purchases on all devices.

This is not Family sharing by the way. Just Apple ID sharing.