Sharing diff users & diff computers

Have 2 users and 2 macs in house & 2 iPhones. One 'main' iCloud account with a secondary iCloud account so user #2 can sync their own calendar & contacts. We set things this way because of the confusion we first encountered with combined addresses, etc. We are finding it more important that we sync our calendars so we would like to go back to syncing our whole setup under 1 iCloud account again, but still keep some things separate. Does anyone have a good site that explains how to do this in the most efficient way so that there is no loss of info, etc.