What's the difference between "census" and "census family"?
Facts in RM can be individual facts or family facts. For the built-in fact types, most of them are individual facts (birth, death, burial, etc.). A few of the built-in fact types are family facts, and a better name for them in some ways would be spouse facts (marriage, divorce, etc.). Individual facts in RM become linked to INDI records in GEDCOM, and family facts become linked to FAM records in GEDCOM. The FAM mechanism in GEDCOM includes FAMS (family spouse) and FAMC (family child) tags. It's best to think of RM's family facts as being associated to the FAMS tag in GEDCOM (the spouses) and not being associated with the FAMC tag in GEDCOM (the children) at all.
You can define your own fact types, and you can define individual fact types or family fact types. After a new fact type is defined as individual or family, individual fact types can't be changed to family and family fact types cannot be changed to individual. This individual and family fact types have nothing to do with sharing of facts. For example, marriage is a family fact type, not an individual fact type that is shared between the two partners.
I don't think the RM developers expected anybody ever to use the "census family" fact type and I suspect it was included only because it's included in the GEDCOM standard. It definitely does not serve as a way to enter a census entry for entire family grouping one time and then to have that one data entry apply to the whole family including children. It's like a marriage fact in that respect. A marriage is important to the children who are the issue of that marriage, but it's not their fact. It's the parents' fact.
Census needs to be entered either as a totally different fact for each member of the family grouping, or else it needs to be entered as a single fact for the head of household and then to share that census fact with each of the other family members.
Shared facts need to be understood thoroughly before you start using them. They involve roles and only one person may have the role of "principle" (i.e. the "main" person for the fact). Everybody else sharing the fact has to have some other role. For example, a birth fact might sometimes be shared with the midwife who delivered the baby. That doesn't mean that the midwife was born the same day as the baby. It means that the midwife delivered the baby. So a birth sentence for John Doe might say "John Doe was born on 12 July 1852". The shared sentence for the same fact for the midwife might say "Sarah Smith was the midwife who delivered John Doe on 12 July 1852". So you can share the individual census fact for the head of household with the other family members who were enumerated in the census at the same time (and a lot of RM users do so), but you have to think carefully how you want such shared sentences to look in reports when they appear for the sharees. For example, the sentence template for the midwife sentence would be something like [ThisPerson] was the midwife who delivered [Person] on [Date]. [ThisPerson] is the sentence template variable for the sharer and [Person] is the sentence template variable for the sharee.