WEp1 for Shopping Center

Hello all, We have a shopping center interested in certification with 10 buildings. Only 3 buildings will have restroom facilities for the retail customers that is meant to serve the entire project (and is approved as meeting code as such). We are not sure how to do the WEp1 calculation. Our original thought is to do a water calculation according to the water use of the retail customers in each building even if the building does not have the restroom facilities. For example, Building A does not have restrooms, but we will still include a water reduction calculation base on the 114 transients using the restroom facilities in Building B. And Building B will only count the water usage of its transients and not the transients of any other building. Is this an acceptable approach? Thanks in advance.