Determining the scope in nonprofit organization

I work for a alcohol and drug rehabilitation centre. We are a not for profit organisation and our funding bodies determine the services that we must provide and the KPIs associated with it. In terms of interested parties (Context of the organisation) my CEO believes that basically the funding bodies are the only interested parties and feels that Suppliers, contractors, cients, employees etc. are not considered interested parties relevant to the QMS. I believe they are because our employees deliver a service to our clients and their needs are proper training, proper communication, resources such as electronic QMS management programs etc. Our suppliers have a direct input on our QMS for example if our IT systems are not running smoothly it causes time delays, loss of information etc. These are just examples. Could you please assist with clarity on who we have to consider as "interested parties".