Usually the AAA breakfast rate includes just 2 breakfasts. If they don't have a Regency club, or it's closed, you will get full breakfast for every registered guest in your room as a Diamond.

As for the suites, in my experience most have a King (or Queen) in the bedroom and a sofa bed in the living area. I would ask if the suites have a sofa bed for the children or if it can accommodate 2 rollaway beds.

You should not have a problem using the Hyatt Check Certificates from Costco at either property.