What options are available to those who have set up units for family as well as rentals and what can the HOA do to us legally?

You are asking whether the HOA is stopped from enforcing its rules because of a five year lapse in doing so. I am not sure, but likely not because the home owners knew what they were doing was in violation of the rules and that at some point the rules would be enforced. If a city does not enforce anti-littering laws for years and then does, it would not be barred from doing so. But if a landlord let a tenant smoke for years and then tries to ban it they might not be able to because it is merely a contractual term and not a law. HOA rules are also contractual terms, but each member of the HOA has the right to enforce those rules. If a new buyer moves in knowing what the rules are, why should he not be entitled to enforce the rules even those before him did not?